JP-3513: Remove warning about inaccurate errors

[penaguerrero]

Resolves JP-3513

Closes #8204

This PR addresses removal of unnecessary warning when weight_type is set to 'exptime':
"Use of EXPTIME weighting will result in incorrect propagated errors in the resampled product". Errors are propagated identically for the 'exptime' and 'ivm' weight options.

The message is benign, but it has been asked about in helpdesk questions, and might unnecessarily deter users from using 'exptime' weights in place of 'ivm'.

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 75.65%. Comparing base (4179c09) to head (969cfd9).
Report is 321 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #8258       +/-   ##
===========================================
+ Coverage   57.97%   75.65%   +17.67%     
===========================================
  Files         387      477       +90     
  Lines       38830    39651      +821     
===========================================
+ Hits        22513    29998     +7485     
+ Misses      16317     9653     -6664     

Flag	Coverage Δ		*Carryforward flag
nightly	77.66% <ø> (?)		Carriedforward from 7d15aaf

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[mcara]

One more thing would make this PR perfect: set default weight to exptime, especially given that #7563 still hasn't been approved.

[hbushouse]

This should not be merged until there's consensus as to whether the warning message is accurate (i.e. I don't think it's benign, as has been suggested).

[melanieclarke]

@hbushouse @drlaw1558 - can this one be merged, now that error propagation for exptime and ivm weights are handled self-consistently (#8437)?

[drlaw1558]

@melanieclarke Seems reasonable to me as the entire point of all of that work was to fix the error propagation! @hbushouse 's call though.

[hbushouse]

One more thing would make this PR perfect: set default weight to exptime, especially given that #7563 still hasn't been approved.

That's going to be done via the use of parameter reference files for the resample/resample_spec steps, where each instrument/mode will choose to set the default to 'exptime' if they want. There are still one or more modes where 'ivm' seems to be preferred.

[hbushouse]

Changes are straight-forward enough and only involve log messages, so I don't see the need for a regression test run.