import GriddedPSFModel from photutils.psf

[braingram]

This PR updates the remaining GriddedPSFModel imports from photutils to prefer importing from the psf submodule to avoid deprecation warnings issued when importing from the top level photutils module.

The modifications here are equivalent to the existing try/except found in gridded_library.py:

webbpsf/webbpsf/gridded_library.py

Lines 113 to 120 in be74228

	# Before doing anything else, check that we have GriddedPSFModel
	try:
	from photutils.psf import GriddedPSFModel
	except ImportError:
	try:
	from photutils import GriddedPSFModel
	except ImportError:
	raise ImportError("This method requires photutils >= 0.6")

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files	Coverage Δ
webbpsf/gridded_library.py	76.92% <100.00%> (ø)
webbpsf/utils.py	57.93% <100.00%> (ø)

📢 Thoughts on this report? Let us know!.

[obi-wan76]

Looks good.

[BradleySappington]

@braingram - please rebase to get the CI legacy test fix