Fix PDBQT docs to accurately say that last letter of segid is used as chainID

[lilyminium]

Fixes #4287

Changes made in this Pull Request:

• Updates last to say first

PR Checklist

• Tests?
• Docs?
• CHANGELOG updated?
• Issue raised/referenced?

Developers certificate of origin

• 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--4288.org.readthedocs.build/en/4288/

[github-actions]

Linter Bot Results:

Hi @lilyminium! Thanks for making this PR. We linted your code and found the following:

There are currently no issues detected! 🎉

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (16647cb) 93.40% compared to head (10768e4) 93.40%.

Additional details and impacted files

@@            Coverage Diff             @@
##           develop    #4288     +/-   ##
==========================================
  Coverage    93.40%   93.40%             
==========================================
  Files          170      184     +14     
  Lines        22250    23358   +1108     
  Branches      4071     4071             
==========================================
+ Hits         20783    21818   +1035     
- Misses         951     1024     +73     
  Partials       516      516             

Files Changed	Coverage Δ
package/MDAnalysis/coordinates/PDBQT.py	83.50% <ø> (ø)

... and 14 files with indirect coverage changes

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[tylerjereddy]

Straightforward fix, thanks