Allow wcslib to "fix" the headers

This allows it to compute MJD-OBS from DATE-OBS, which is needed to work
around astropy/astropy#11248. Unfortunately
that also means that FITS files with OBSGEO-X/Y/Z headers will spew out
warnings due to astropy/astropy#10365, but
that's better than crashing.

katsdpimageutils/render.py

@@ -132,8 +132,7 @@ def write_image(input_file, output_file, width=1024, height=768, dpi=DEFAULT_DPI
     """
 
     with fits.open(input_file) as hdus:
-        # Fixing disabled due to https://github.com/astropy/astropy/issues/10365
-        wcs = WCS(hdus[0], fix=False)
+        wcs = WCS(hdus[0])
         if slices is None:
             slices = ('x', 'y') + (0,) * (wcs.pixel_n_dim - 2)
         ax_select = tuple(slice(None) if s in ('x', 'y') else s for s in slices[::-1])