JP-3527 Update to docs for IFU outlier detection

[jemorrison]

Resolves JP-3527

Closes #8250

This PR updates the IFU outlier docs. I also updated some comments in the ifu_outlier code to make things more clear.

Checklist for maintainers

• added entry in CHANGES.rst within the relevant release section
• updated or added relevant tests
• updated relevant documentation
• added relevant milestone
• added relevant label(s)
• ran regression tests, post a link to the Jenkins job below.
  How to run regression tests on a PR
• Make sure the JIRA ticket is resolved properly

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.35%. Comparing base (2fb073e) to head (e289857).
Report is 1 commits behind head on master.

❗ Current head e289857 differs from pull request most recent head a498ca2. Consider uploading reports for the commit a498ca2 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8360      +/-   ##
==========================================
+ Coverage   75.31%   75.35%   +0.04%     
==========================================
  Files         474      474              
  Lines       38965    38944      -21     
==========================================
+ Hits        29345    29348       +3     
+ Misses       9620     9596      -24     

Flag	Coverage Δ		*Carryforward flag
nightly	77.33% <ø> (-0.01%)	⬇️	Carriedforward from 4cc0ac1

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[hbushouse]

@jemorrison If you can address the review comments we can get this merged.

[jemorrison]

@hbushouse Changes from review have been made