gh-91423: Remove bugs.python.org from bugs.rst (GH-91425)

* Remove bugs.python.org from bugs.rst

* Update bugs.rst to the github issue tracker

* reflow

* Fix a typo and rephrase a sentence.

Co-authored-by: Inada Naoki <songofacandy@gmail.com>
Co-authored-by: Ezio Melotti <ezio.melotti@gmail.com>