doc: fix typo in writing-test.md

Corrects the misspelling of "optimial" to "optimal".

PR-URL: #59123
Reviewed-By: Filip Skokan <[email protected]>
Reviewed-By: Gireesh Punathil <[email protected]>
Reviewed-By: Darshan Sen <[email protected]>
Reviewed-By: Rafael Gonzaga <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Ulises Gascón <[email protected]>

Author: SeokhunEom

doc/contributing/writing-tests.md

@@ -24,7 +24,7 @@ See [directory structure overview][] for outline of existing test and locations.
 
 ## How to write a good test
 
-A good test should be written in a style that is optimial for debugging
+A good test should be written in a style that is optimal for debugging
 when it fails.
 
 In principle, when adding a new test, it should be placed in a new file.