docs mention saving to AsdfInFits which is not available in asdf 3.0

[braingram]

Perhaps this section should be removed?

gwcs/docs/index.rst

Line 250 in 929478d

>>> from asdf import fits_embed

Or alternatively the section could be updated to use stdatamodels:
https://stdatamodels.readthedocs.io/en/latest/asdf_in_fits.html#writing-asdfinfits-files

[perrygreenfield]

Does the reading of the WCS from a FITS extension still work (line 260)?

[braingram]

Neither reading nor writing to fits works with asdf 3.0 as support for AsdfInFits was dropped.

Which line are you referring to for reading of the WCS from a FITS extension? Line 260 in docs/index.rst appears to be writing to a fits extension. Are you referring to a different file?

gwcs/docs/index.rst

Lines 259 to 261 in 929478d

	>>> fa = fits_embed.AsdfInFits(hdul, tree)
	>>> fa.write_to("imaging_with_wcs_in_asdf.fits")
	>>> fits.info("imaging_with_wcs_in_asdf.fits")

The following section in docs/index.rst that refers to reading from a fits extension (using asdf) is another example of something that no longer works in asdf 3.0:

gwcs/docs/index.rst

Lines 283 to 288 in 929478d

	.. doctest-skip::
	>>> import asdf
	>>> fa = asdf.open("imaging_with_wcs_in_asdf.fits")
	>>> wcsobj = fa.tree["wcs"]

[perrygreenfield]

For now I just removed all that FITS stuff (both reading and writing examples from and to FITS extensions). I'd rather not pull in stdatamodels in this. If we have a more generic way of dealing with ASDF in FITS extensions, we can but it back in, but for now let's leave it out.

[perrygreenfield]

Addressed by #483