LGPL switch

[IAlibay]

As per https://www.mdanalysis.org/2023/09/22/licensing-update/#detailing-our-proposed-relicensing-process

We are now at step 3, where we package under LGPLv3+ until we remove our apache dependencies.

Changes made in this Pull Request:

• [x] Update LICENSE files (LGPLv3+)
• [x] Update all code references of GPLv2+ to LGPLv2.1+

PR Checklist

• [ ] Tests?
• [x] Docs?
• [x] CHANGELOG updated?
• [ ] Issue raised/referenced?

Developers certificate of origin

• [x] I certify that this contribution is covered by the LGPLv2.1+ license as defined in our LICENSE and adheres to the Developer Certificate of Origin.

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📚 Documentation preview 📚: https://mdanalysis--4794.org.readthedocs.build/en/4794/

[codecov[bot]]

Codecov Report

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

Project coverage is 93.64%. Comparing base (b254921) to head (ffe8371). Report is 2 commits behind head on develop.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #4794 +/- ## =========================================== - Coverage 93.66% 93.64% -0.03% =========================================== Files 177 189 +12 Lines 21742 22808 +1066 Branches 3055 3055 =========================================== + Hits 20365 21358 +993 - Misses 930 1003 +73 Partials 447 447 ```

:umbrella: View full report in Codecov by Sentry.
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🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests

[IAlibay]

Thanks @orbeckst I just added the text because "why not" and centered the LGPLv3 header.

[orbeckst]

@MDAnalysis/coredevs the license change has been approved by final vote and we will merge this PR in order to switch the license of MDAnalysis to LGPL (as detailed above).

Thank you everyone for their support in this 3-year long process.