Remove Python 3.7

[schlenk]

• [x] Any changes relevant to users are recorded in the CHANGELOG.md.

• [x] The documentation has been updated, if necessary.

• [ ] New code is annotated.

• [ ] Changes are covered by tests.

• Removed Python 3.7 Build as required build from Branch Protection

• Fixed readthedocs configuration

• Updated Versions in CI config and setup

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 63.80%. Comparing base (0e30cd2) to head (f0e8046).

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #870 +/- ## ========================================== - Coverage 63.83% 63.80% -0.04% ========================================== Files 64 64 Lines 11879 11879 Branches 2107 2155 +48 ========================================== - Hits 7583 7579 -4 - Misses 3693 3697 +4 Partials 603 603 ```

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