JP-3465: removed product exposure time TEXPTIME

[emolter]

Partially resolves JP-3465

This PR addresses removal of the TEXPTIME (product exposure time) keyword, since it is functionally redundant with XPOSURE and EFFEXPTM and is not used by any high-level data processing scripts we know about.

Checklist

• added entry in CHANGES.rst (either in Bug Fixes or Changes to API)
• updated relevant tests
• updated relevant documentation
• updated relevant milestone(s)
• added relevant label(s)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 64.70%. Comparing base (4d7c3a6) to head (f593a25).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #277      +/-   ##
==========================================
- Coverage   64.84%   64.70%   -0.14%     
==========================================
  Files         103      104       +1     
  Lines        5694     5701       +7     
==========================================
- Hits         3692     3689       -3     
- Misses       2002     2012      +10     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[braingram]

It looks like spacetelescope/jwst#8212 removes the 2 uses in jwst.

Given the separate packages how should this PR be coordinated to avoid errors?

The current jwst dev pins stdatamodels to:
stdatamodels>=1.10.0,<1.11.0
all released version have pins <1.10 so this PR (which is targeting 1.10.1) will not impact any released versions of jwst. I think that means if we:

• merge the jwst PR first, this should fix the CI here
• merge this PR

will we see any issues?

[hbushouse]

LGTM

[hbushouse]

We should merge the changes to the jwst repo first, so that the pipeline code no longer tries accessing the keyword attribute, before we remove it from the datamodel schema here.

[hbushouse]

spacetelescope/jwst#8212 has been merged, so it should be safe to merge this PR now. We'll need to update stdatamodels pins over in jwst once there's a new stdatamodels release.