Merge pull request #293 from juanfra/fix/contributing-md

Fix markup in contributing.md

Co-authored-by: juanfra <juanfra@git.wordpress.org>

Author: jeffpaul

CONTRIBUTING.md

@@ -48,6 +48,7 @@ composer format && npm run lint:js:fix
 
 # Run tests
 npm run test:e2e:env:start && npm run test:e2e && npm run test:php && npm run test:e2e:env:stop
+```
 
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