Fix spelling error in CONTRIBUTING.md

[Voultapher]

Thought I'd start with something small.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @aturon (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[Voultapher]

The build errors seem unrelated. Would be highly surprising if this change would break anything.

[kennytm]

@bors r+ rollup

[bors]

📌 Commit 0bc8d4e has been approved by kennytm

[bors]

⌛ Testing commit 0bc8d4e with merge 6a2d682486c5bb435836623dff34d991c0178405...

[bors]

💔 Test failed - status-travis

[rust-highfive]

The job x86_64-gnu-aux of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

  0     0    0     0    0     0      0      0 --:--:--  0:00:51 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:52 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:53 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:54 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:55 --:--:--     0curl: (6) Could not resolve host: s3-us-west-1.amazonaws.com
[01:44:52] thread 'main' panicked at 'failed to download openssl source: exit code: 6', bootstrap/native.rs:575:17
[01:44:52] note: Run with `RUST_BACKTRACE=1` for a backtrace.
[01:44:52] make: *** [check-aux] Error 1
[01:44:52] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/test/pretty src/test/run-pass/pretty src/test/run-fail/pretty src/test/run-pass-valgrind/pretty src/test/run-pass-fulldeps/pretty src/test/run-fail-fulldeps/pretty src/tools/cargo src/tools/cargotest
[01:44:52] Build completed unsuccessfully in 0:18:03
[01:44:52] Makefile:60: recipe for target 'check-aux' failed

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:12511e8f
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[rust-highfive]

The job x86_64-gnu-aux of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

  0     0    0     0    0     0      0      0 --:--:--  0:00:51 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:52 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:53 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:54 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:55 --:--:--     0curl: (6) Could not resolve host: s3-us-west-1.amazonaws.com
[01:44:52] thread 'main' panicked at 'failed to download openssl source: exit code: 6', bootstrap/native.rs:575:17
[01:44:52] note: Run with `RUST_BACKTRACE=1` for a backtrace.
[01:44:52] make: *** [check-aux] Error 1
[01:44:52] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/test/pretty src/test/run-pass/pretty src/test/run-fail/pretty src/test/run-pass-valgrind/pretty src/test/run-pass-fulldeps/pretty src/test/run-fail-fulldeps/pretty src/tools/cargo src/tools/cargotest
[01:44:52] Build completed unsuccessfully in 0:18:03
[01:44:52] Makefile:60: recipe for target 'check-aux' failed

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:12511e8f
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[kennytm]

@bors retry travis-ci/travis-ci#9696? One hour too late though

[bors]

⌛ Testing commit 0bc8d4e with merge a561ea7...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: kennytm
Pushing a561ea7 to master...