getting rid of lexsort warning

[atharva-2001]

This is an attempt to get rid of PerformanceWarning: indexing past lexsort depth may impact performance

Description

I tried creating a new column of wavelengths with CGS units in a different way. This way was just a little bit faster and
also got rid of the WARNING. The results were the same as well.
Using the new way, I got this:
Simulation finished in 20 iterations and took 35.58 s (base.py:381)

and using the previous way I got this:
Simulation finished in 20 iterations and took 35.70 s (base.py:381)

Motivation and Context

This got rid of the PerformanceWarning: indexing past lexsort depth may impact performance.

How Has This Been Tested?

• Testing pipeline
• Reference Data Comparison following these instructions
• Other (please describe)

Using python setup.py test I got 156 passed, 1254 skipped, 6 xpassed in 4.95s
The notebooks are working fine as well.

Screenshots:

Before

After

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• None of the above (please describe)

Checklist:

• My code follows the code style of this project
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have built the documentation on my fork following these instructions
• I have assigned and requested two reviewers for this pull request

[atharva-2001]

@wkerzendorf would you mind reviewing it, please?

[codecov]

Codecov Report

Merging #1479 (1dbaf59) into master (9497250) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1479   +/-   ##
=======================================
  Coverage   71.13%   71.13%           
=======================================
  Files          67       67           
  Lines        5523     5523           
=======================================
  Hits         3929     3929           
  Misses       1594     1594           

Impacted Files	Coverage Δ
tardis/tardis/io/atom_data/base.py	91.17% <0.00%> (ø)

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