fix setting plot options state when setting cmap through API

[kecnry]

Description

This pull request fixes setting the plot options state for colormap when set through the API (either by manually setting the glue-state or through the astrowidgets API).

Fixes #1506

Checklist for package maintainer(s)

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• After merge, any internal documentations need updating (e.g., JIRA, Innerspace)?

[codecov]

Codecov Report

Merging #1507 (e82a0c3) into main (d24f823) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1507   +/-   ##
=======================================
  Coverage   85.46%   85.46%           
=======================================
  Files          91       91           
  Lines        8551     8551           
=======================================
  Hits         7308     7308           
  Misses       1243     1243           

Impacted Files	Coverage Δ
jdaviz/core/template_mixin.py	91.43% <100.00%> (ø)

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[pllim]

Works if the Color Mode stays in Colormap mode, which I think that this PR wants to fix.

But we should open a follow up ticket for bug of viewer.set_colormap('Viridis') not updating Plot Options when Color Mode is in Monochromatic mode, which might be related to #1504 .

Thanks for the quick fix!

[pllim]

Follow-up issue at #1510