bpo-37936: Remove some .gitignore rules that were intended locally. (GH-15542)

bpo-37936: Remove some .gitignore rules that were intended locally. (GH-15542)

These appeared in commit c5ae169e1.  The comment on them, as well as
the presence among them of a rule for the .gitignore file itself,
indicate that the author intended these lines to remain only in their
own local working tree -- not to get committed even to their own repo,
let alone merged upstream.

They did nevertheless get committed, because it turns out that Git
takes no notice of what .gitignore says about files that it's already
tracking... for example, this .gitignore file itself.

Give effect to these lines' original intention, by deleting them. :-)

Git tip, for reference: the `.git/info/exclude` file is a handy way
to do exactly what these lines were originally intended to do.  A
related handy file is `~/.config/git/ignore`.  See gitignore(5),
aka `git help ignore`, for details.

https://bugs.python.org/issue37936

Automerge-Triggered-By: @zware
(cherry picked from commit 8c9e9b0cd5b24dfbf1424d1f253d02de80e8f5ef)

Co-authored-by: Greg Price <gnprice@gmail.com>