Fix FileExistsError in to_hdf()

[yuyizheng1112]

Fix #1624.

How has this been tested?

• Testing pipeline.
• Other.

Examples
Before the change:

After the change:

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.

[codecov]

Codecov Report

Merging #1630 (012af2a) into master (e062c69) will decrease coverage by 5.26%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1630      +/-   ##
==========================================
- Coverage   67.20%   61.94%   -5.27%     
==========================================
  Files          73       62      -11     
  Lines        6150     5728     -422     
==========================================
- Hits         4133     3548     -585     
- Misses       2017     2180     +163     

Impacted Files	Coverage Δ
tardis/tardis/util/base.py	75.78% <0.00%> (-1.99%)	⬇️
tardis/tardis/montecarlo/montecarlo_numba/base.py	28.73% <0.00%> (-0.90%)	⬇️
tardis/tardis/simulation/base.py	85.16% <0.00%> (-0.47%)	⬇️
tardis/tardis/scripts/cmfgen2tardis.py	0.00% <0.00%> (ø)
tardis/tardis/montecarlo/packet_source.py	97.29% <0.00%> (ø)
tardis/tardis/plasma/properties/atomic.py	61.76% <0.00%> (ø)
...dis/montecarlo/montecarlo_numba/tests/test_base.py
...s/montecarlo/montecarlo_numba/tests/test_packet.py
...tecarlo/montecarlo_numba/tests/test_interaction.py
...rdis/montecarlo/montecarlo_numba/tests/conftest.py
... and 15 more

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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.

[jaladh-singhal]

Excellent catch @yuyizheng1112 - thanks for fixing it!