remove Python 3.7

[semuadmin]

pyubx2 Pull Request Template

Description

Python 3.7 is officially end of life on 27 June 2023. This change removes Python 3.7 from workflows and documentation.

Testing

Please test all changes, however trivial, against the supplied pytest suite tests/test_*.py. Please describe any test cases you have amended or added to this suite to maintain >= 99% code coverage.

If you're adding new UBX message definitions for Generation 9+ devices, please check for any corresponding configuration database updates (ubxtypes_configdb.py).

Checklist:

• [x] I agree to abide by the code of conduct (see CODE_OF_CONDUCT.md).
• [x] My code follows the style guidelines of this project (see CONTRIBUTING.MD).
• [x] I have performed a self-review of my own code.
• [x] (if appropriate) I have cited my u-blox documentation source(s).
• [x] I have commented my code, particularly in hard-to-understand areas.
• [x] I have made corresponding changes to the documentation.
• [x] (if appropriate) I have added test cases to the tests/test_*.py unittest suite to maintain >= 99% code coverage.
• [x] I have tested my code against the full tests/test_*.py unittest suite.
• [x] My changes generate no new warnings.
• [x] Any dependent changes have been merged and published in downstream modules.
• [x] I have signed my commits.
• [x] I understand and acknowledge that the code will be published under a BSD 3-Clause license.