remove unused gwcs_types

[braingram]

The gwcs_types submodule is unused and uses the deprecated extension api in asdf. This will create warnings in asdf 2.15 and fail to work with asdf 3.0 as is described in #441

This PR removes gwcs_types.

fixes #441

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.09 ⚠️

Comparison is base (2e39161) 86.95% compared to head (4c7937e) 86.87%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #443      +/-   ##
==========================================
- Coverage   86.95%   86.87%   -0.09%     
==========================================
  Files          25       24       -1     
  Lines        3895     3871      -24     
==========================================
- Hits         3387     3363      -24     
  Misses        508      508              

Flag	Coverage Δ
unit	86.87% <ø> (-0.09%)	⬇️

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[braingram]

The jwst CI job failure appears in a file in scripts:
https://github.com/spacetelescope/gwcs/actions/runs/4304658164/jobs/7505997639#step:12:280
This directory is ignored in the jwst tests:
https://github.com/spacetelescope/jwst/blob/4285c4efb95bc368f36456e9e106e6aba6abd597/setup.cfg#L152
Likely the CI job here in gwcs should be updated to exclude testing these files. EDIT: see #444

[mcara]

Looks good to me. Test failure (pointing_summary) is unrelated.