Fixing RST Formatting for config_validator.rst

[DhruvSondhi]

Fixing general formatting issues with the config validator documentation

Description
Changes have been made to the rst formatting done in the config_validator documentation.
This makes the documentation easier to read & understand. :)

Motivation and context
As the documentation is quite old, changes to the formatting must also be done so as to bring it at par to current standards.
Simple fixes for the formatting have been done ... Furthermore, I will be opening PR for all the documentation formatting that can be done. :)

How has this been tested?

• Testing pipeline.
• Other.
  • Local Testing

Screenshot

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 #1553 (2bb485b) into master (c384d74) will decrease coverage by 1.28%.
The diff coverage is n/a.

❗ Current head 2bb485b differs from pull request most recent head 5dc73bd. Consider uploading reports for the commit 5dc73bd to get more accurate results

@@            Coverage Diff             @@
##           master    #1553      +/-   ##
==========================================
- Coverage   68.24%   66.95%   -1.29%     
==========================================
  Files          73       73              
  Lines        6373     6034     -339     
==========================================
- Hits         4349     4040     -309     
+ Misses       2024     1994      -30     

Impacted Files	Coverage Δ
...ntecarlo/montecarlo_numba/frame_transformations.py	35.00% <0.00%> (-13.00%)	⬇️
...s/tardis/montecarlo/montecarlo_numba/estimators.py	43.75% <0.00%> (-8.89%)	⬇️
...montecarlo/montecarlo_numba/calculate_distances.py	23.07% <0.00%> (-7.16%)	⬇️
.../tardis/montecarlo/montecarlo_numba/interaction.py	28.20% <0.00%> (-5.13%)	⬇️
.../montecarlo/montecarlo_numba/single_packet_loop.py	27.11% <0.00%> (-3.53%)	⬇️
...is/tardis/montecarlo/montecarlo_numba/opacities.py	80.00% <0.00%> (-3.34%)	⬇️
...dis/tardis/montecarlo/montecarlo_numba/r_packet.py	25.21% <0.00%> (-2.44%)	⬇️
...rdis/tardis/montecarlo/montecarlo_numba/vpacket.py	17.47% <0.00%> (-2.34%)	⬇️
tardis/tardis/plasma/properties/util/macro_atom.py	29.03% <0.00%> (-2.22%)	⬇️
...rdis/montecarlo/montecarlo_numba/tests/conftest.py	91.11% <0.00%> (-1.88%)	⬇️
... and 39 more

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[isaacgsmith]

It looks good!

[KevinCawley]

Nice work