Update CONTRIBUTING.md (#2601)

CONTRIBUTING.md

 in the agreement, unfortunately, we cannot accept your contribution.
 
 ## Creating Pull Requests
-- Make sure your code passes the linter rules beforehand. The linter is exeuted
+- Make sure your code passes the linter rules beforehand. The linter is executed
   automatically when committing code.
 - Perform **one** logical change per pull request.
 - Maintain a clean list of commits, squash them if necessary.