[doc] Fix typo and formatting in CONTRIBUTING.md #34729

Job	Run time
build (windows-latest)	5m 11s
build (ubuntu-latest)	1m 54s
build (macos-latest)	4m 39s
check-bevy-internal-imports	4s
check-doc	5m 21s
check-missing-examples-in-docs	30s
ci	1m 50s
miri	6m 47s
run-examples-on-windows-dx12	14m 11s
toml	9s
check-missing-features-in-docs	26s
markdownlint	1m 14s
check-compiles	2m 19s
build-wasm	41s
msrv	51s
	46m 7s

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