Remove the default value for the test_suffix parameter (#64)

Passing a comma-separated list of values to the CLI argument
--test-suffix has been deprecated in PHPUnit 11[1] and will no longer
work in PHPUnit 12.  Given that this action is sending its default
value[2] anyways, there's no reason to explicitly provide this command
line argument.  Further, it's confusing that this command line argument
is specified at all when nothing in my repo's configuration sets its
value.

[1]: sebastianbergmann/phpunit#5709
[2]: https://docs.phpunit.de/en/11.1/textui.html#selection

Author: cookieguru

action.yml

@@ -67,7 +67,6 @@ inputs:
   test_suffix:
     description: Only search for test in files with specified suffix(es)
     required: false
-    default: Test.php,.phpt
 
   whitelist:
     description: Path to directory to whitelist for code coverage analysis