graphics/py-pytesseract: update to 0.3.9

Release Notes: https://github.com/madmaze/pytesseract/releases/tag/v0.3.9

• bump minimal Python requirement to 3.7, upstream de-supports EOL 3.6
• upstream made build tweaks

Packager Notes:

• test_image_to_data_common_output[dict] is failing for me, => https://github.com/madmaze/pytesseract/issues/406

• if your tox package complains it cannot find py-filelock, update the latter to 3.4.2_1 (commit 97cae4aba by yuri@ 2022-01-19)