Remove cargo-fmt and rustfmt-bin from self_tests()

[dlukes]

cargo test currently fails with:

---- self_tests stdout ----
	thread 'self_tests' panicked at 'Couldn't read file ../cargo-bin/src/main.rs: Os { code: 2, kind: NotFound, message: "No such file or directory" }', libcore/result.rs:945:5
note: Run with `RUST_BACKTRACE=1` for a backtrace.

and

---- self_tests stdout ----
	thread 'self_tests' panicked at 'Couldn't read file ../rustfmt-bin/src/main.rs: Os { code: 2, kind: NotFound, message: "No such file or directory" }', libcore/result.rs:945:5
note: Run with `RUST_BACKTRACE=1` for a backtrace.

I suppose in light of 9d2229f, self_tests() should be updated?

[nrc]

Yes, thank you!