Remove file check for pytmdb3.cache

This is a partial roll back of 2c50a824b and remove the check for the
pytmdb3.cache file, allowing the library to simply create the file if
necessary.

Fixes #11876

(cherry picked from commit ec084b39099d2ea43a736ac46caffad90272ef9d)

Conflicts:
	mythtv/programs/scripts/metadata/Movie/tmdb3.py