Fix Python.gitignore for celery-beat

[gsilvan]

Reasons for making this change

celery beat creates the following 3 files for running celery -A sampleproject worker -B --loglevel=INFO.

$ file celerybeat-schedule*
celerybeat-schedule:     SQLite 3.x database, last written using SQLite version 3047001, writer version 2, read version 2, file counter 2, database pages 3, cookie 0x1, schema 4, UTF-8, version-valid-for 2
celerybeat-schedule-shm: SQLite Write-Ahead Log shared memory, counter 10, page size 4096, 20 frames, 3 pages, frame checksum 0x7f59ff13, salt 0x55b59b42d325d3a6, header checksum 0xa485f19a, read-mark[1] 0x14
celerybeat-schedule-wal: SQLite Write-Ahead Log, version 3007000

The current .gitignore ignores only celerybeat-schedule. This PR adds support to cover all files added per default by celery-beat.

Links to documentation supporting these rule changes

https://docs.celeryq.dev/en/v5.5.2/reference/cli.html#cmdoption-celery-beat-s https://github.com/search?q=celerybeat-schedule*&type=code

Merge and Approval Steps

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