Fix duplicate level for `trajectory-similarity` level

[mhmohona]

Fix duplicate level for trajectory-similarity level by updating the tag.

Close #375

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📚 Documentation preview 📚: https://mdanalysisuserguide--386.org.readthedocs.build/en/386/

[RMeli]

Hi @mhmohona, I don't think this solves the issue, does it? CI still shows the error, with the new tag:

/home/runner/work/UserGuide/UserGuide/doc/source/examples/analysis/trajectory_similarity/README.rst:6: WARNING: duplicate label trajectory-similarity-analysis, other instance in /home/runner/work/UserGuide/UserGuide/doc/source/examples/analysis/README.rst

https://github.com/MDAnalysis/UserGuide/actions/runs/11045817485/job/30684095342?pr=386#step:7:273

[orbeckst]

@mhmohona do you have the time to come back to this PR or should we close it?

[mhmohona]

@orbeckst,I will work on it. However I had some confusion here, thus marked it as draft.

[orbeckst]

The build still shows the warning

/home/runner/work/UserGuide/UserGuide/doc/source/examples/analysis/trajectory_similarity/README.rst:6: WARNING: duplicate label trajectory-similarity-overview, other instance in /home/runner/work/UserGuide/UserGuide/doc/source/examples/analysis/README.rst