PR title: regex fix

old version prohibited first word to finish with `s` char, that is quite a weird

.github/workflows/check_pull_request_title.yml

@@ -16,6 +16,6 @@ jobs:
           # - "Do something."
           # - "Does something"
           # - "Do"
-          regex: '^[A-Z][a-zA-Z]*(?<!s)( [a-zA-Z]+)+[^.]$'  # use regex101.com for explanation
+          regex: '^[A-Z][a-zA-Z]*( [a-zA-Z]+)+[^.]$'  # use regex101.com for explanation
           min_length: 10
           max_length: 72