PR Summary

The updates to scalar mappable would only occur if the
array was updated. This meant that updating the vmin/vmax of
the sm's norm would not be propagated to the drawn artists. This
update removes the array update checks from scalar mappable to calculate
the colors regardless of updates to the array.

PR Checklist

• Has pytest style unit tests (andpytest passes).
• IsFlake 8 compliant (runflake8 on changed files to check).
• [N/A] New features are documented, with examples if plot related.
• [N/A] Documentation is sphinx and numpydoc compliant (the docs shouldbuild without error).
• [N/A] Conforms to Matplotlib style conventions (installflake8-docstrings and runflake8 --docstring-convention=all).
• New features have an entry indoc/users/next_whats_new/ (follow instructions in README.rst there).
• API changes documented indoc/api/next_api_changes/ (follow instructions in README.rst there).