testing/py3-flask-caching: upgrade to 1.10.1

Release notes, from https://github.com/sh4nks/flask-caching/releases/tag/v1.10.1:

• A GoogleCloudStorageCache backend has been added to the user contributed caching backends.
• Fix a regression introduced in the last release which broke all applications subclassing the Cache class.
• Add test_generic_get_bytes test case.
• Various improvements and fixes.