Not able to read FITS with `format="iraf"`

Description:

I have a FITS file which is already wavelength calibrated and have spectral world coordinates in the Header. But when I try to read the file using this:
`Spectrum1D.read(specdata.any(), format="iraf") `
I get this error:
```
---------------------------------------------------------------------------
OSError Traceback (most recent call last)
/Users/bhavesh/coding/MSc/mkep5/Ex8.ipynb Cell 7' in ()
----> [1](vscode-notebook-cell:/Users/bhavesh/coding/MSc/mkep5/Ex8.ipynb#ch0000028?line=0) Spectrum1D.read(specdata.any(), format="iraf")

File /Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/astropy/nddata/mixins/ndio.py:59, in NDDataRead.__call__(self, *args, **kwargs)
58 def __call__(self, *args, **kwargs):
---> 59 return self.registry.read(self._cls, *args, **kwargs)

File /Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/astropy/io/registry/core.py:212, in UnifiedInputRegistry.read(self, cls, format, cache, *args, **kwargs)
208 format = self._get_valid_format(
209 'read', cls, path, fileobj, args, kwargs)
211 reader = self.get_reader(format, cls)
--> 212 data = reader(*args, **kwargs)
214 if not isinstance(data, cls):
215 # User has read with a subclass where only the parent class is
216 # registered. This returns the parent class, so try coercing
217 # to desired subclass.
218 try:

File /Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/specutils/io/default_loaders/wcs_fits.py:259, in non_linear_wcs1d_fits(file_obj, **kwargs)
233 @data_loader('iraf', identifier=identify_iraf_wcs, dtype=Spectrum1D, extensions=['fits'])
234 def non_linear_wcs1d_fits(file_obj, **kwargs):
235 """Load Spectrum1D with WCS spectral axis from FITS files written by IRAF
236
...
540 "method, required for mode '{}'.".format(self.mode))
542 # Any mode except for 'ostream' requires readability
543 if self.mode != 'ostream' and not hasattr(self._file, 'read'):

OSError: File-like object does not have a 'write' method, required for mode 'ostream'.
```

I am also attaching the file which I'm trying to import.
[arc_lapm_wav.fits.zip](https://github.com/astropy/specutils/files/8943131/arc_lapm_wav.fits.zip)

I really don't want to do the calibration again. Therefore, any help resolving this issue would be really appreciated.

------------------
System Details:
```
'platform': 'Darwin',
'platform-release': '21.5.0',
'platform-version': 'Darwin Kernel Version 21.5.0,
'architecture': 'arm64',
'processor': 'M1 Pro',
'ram': '16 GB'
'os': 'macOS Montery 12.4'
```

Kernel Details:
```
Python: 3.10.4 64bit
Specutils: 1.7.0
Astropy: 5.1
Numpy: 1.22.4
Matplotlib: 3.5.2
```

Start by reproducing Spectrum1D.read(specdata.any(), format="iraf") with the attached arc_lapm_wav.fits file and the reported Python, specutils, and Astropy versions. Trace the IRAF FITS reader at the location shown in the traceback; done means the file loads successfully while retaining its spectral world coordinates.

Written by the indexing model from the issue text.