Post-History: Recognize discuss.python.org post links without trailin…

…g slash

Previously a URL like the following was recognized:
    https://discuss.python.org/t/typeform-spelling-for-a-type-annotation-object-at-runtime/51435/7/
But the canonical URL actually has no trailing slash:
    https://discuss.python.org/t/typeform-spelling-for-a-type-annotation-object-at-runtime/51435/7
That canonical URL is now recognized.

.pre-commit-config.yaml

@@ -206,7 +206,7 @@ repos:
       - id: validate-post-history
         name: "'Post-History' must be '`DD-mmm-YYYY <Thread URL>`__, ...'"
         language: pygrep
-        entry: '(?<=\n)Post-History:(?:(?! ?\n|((( +|\n {1,14})(([0-2][0-9]|(3[01]))-(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)-(199[0-9]|20[0-9][0-9])|`([0-2][0-9]|(3[01]))-(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)-(199[0-9]|20[0-9][0-9]) <https://((discuss\.python\.org/t/([\w\-]+/)?\d+(?:/\d+/|/?))|(mail\.python\.org/pipermail/[\w\-]+/\d{4}-[A-Za-z]+/[A-Za-z0-9]+\.html)|(mail\.python\.org/archives/list/[\w\-]+@python\.org/thread/[A-Za-z0-9]+/?(#[A-Za-z0-9]+)?))>`__)(,|(?=\n[^ ])))+\n(?=[A-Z\n]))))'
+        entry: '(?<=\n)Post-History:(?:(?! ?\n|((( +|\n {1,14})(([0-2][0-9]|(3[01]))-(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)-(199[0-9]|20[0-9][0-9])|`([0-2][0-9]|(3[01]))-(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)-(199[0-9]|20[0-9][0-9]) <https://((discuss\.python\.org/t/([\w\-]+/)?\d+(?:/\d+/?|/?))|(mail\.python\.org/pipermail/[\w\-]+/\d{4}-[A-Za-z]+/[A-Za-z0-9]+\.html)|(mail\.python\.org/archives/list/[\w\-]+@python\.org/thread/[A-Za-z0-9]+/?(#[A-Za-z0-9]+)?))>`__)(,|(?=\n[^ ])))+\n(?=[A-Z\n]))))'
         args: [--multiline]
         files: '^peps/pep-\d+\.rst$'