Fixing small docs issues

[isaacgsmith]

Description

This PR:

• Fixes documentation warnings from broken docstrings and hyperlinks.
• Removes an unused HDF file from the docs folder.
• Adds an overwrite option to the arepo export method. This is needed for the documentation as currently rerunning the documentation build will add two extra untracked files every run. This way we will only have two files generated that are added to .gitignore. This is also important for users in general if users want to make changes and re-export the snapshot without cluttering their downloads.

How has this been tested?

• Testing pipeline.
• Other.
  Docs built on GitHub.

Examples

Docs build logs with no warnings: https://github.com/smithis7/tardis/runs/5117973003
Main edited docs page: https://smithis7.github.io/tardis/branch/arepo_warning_fix_doc/io/configuration/components/models/converters/arepo_to_tardis.html

Type of change

• Bug fix.
• New feature.
• Breaking change.
• None of the above.

Checklist

• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
  • (optional) I have built the documentation on my fork following the instructions.
• I have assigned and requested two reviewers for this pull request.

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[tardis-bot]

Before a pull request is accepted, it must meet the following criteria:

• Is the necessary information provided?
• Is this a duplicate PR?
  • If a new PR is clearly a duplicate, ask how this PR is different from the original PR?
  • If this PR is about to be merged, close the original PR with a link to this new PR that solved the issue.
• Does it pass existing tests and are new tests provided if required?
  • The test coverage should not decrease, and for new features should be close to 100%.
• Is the code tidy?
  • No unnecessary print lines or code comments.

[codecov]

Codecov Report

Merging #1893 (1c579df) into master (c705946) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1893   +/-   ##
=======================================
  Coverage   62.55%   62.55%           
=======================================
  Files          68       68           
  Lines        7127     7127           
=======================================
  Hits         4458     4458           
  Misses       2669     2669           

Impacted Files	Coverage Δ
tardis/tardis/io/parsers/arepo.py	69.04% <0.00%> (ø)

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[andrewfullard]

Need to fix the black error in arepo.py