Fixing indent_style control flow examples

[davidalber]

This PR fixes the two control flow snippets for in Configurations.md per the outcome of #2427.

Here is the current output of cargo test -- --ignored on master:

---- configuration_snippet_tests stdout ----
        Ran 106 configurations tests.
thread 'configuration_snippet_tests' panicked at 'assertion failed: `(left == right)`
  left: `6`,
 right: `0`: 6 configurations tests failed', tests/system.rs:800:5

Here is the output of cargo test -- --ignored on the PR branch:

---- configuration_snippet_tests stdout ----
        Ran 106 configurations tests.
thread 'configuration_snippet_tests' panicked at 'assertion failed: `(left == right)`
  left: `4`,
 right: `0`: 4 configurations tests failed', tests/system.rs:800:5

This is part of #1845.

[nrc]

Thanks!