Add ABI dump to .gitignore by encukou · Pull Request #94166 · python/cpython

The ABI is only checked in maintenance branches, but it is sometimes useful to generate it for main.

• The resulting file should be ignored in main.
• The file should be created if it doesn't exist.

If this goes in, some “make maintenance branch” RM checklist/script will need a “remove Doc/data/python*.abi from .gitignore” entry.

@pablogsal, this could be combined with #94135