PVSPEC model coefficients for First Solar modules use wrong keys

[sophie-pelland]

Describe the bug
The function pvlib.spectrum.mismatch.spectral_factor_pvspec has a dictionary of coefficients. These have incorrect keys for the two types of First Solar modules. module types for these are 'fs4-1' and 'fs4-2', but the coefficients have keys 'fs-2' and 'fs-4', which should be 'fs4-2' and 'fs4-1', respectively.

To Reproduce
Steps to reproduce the behavior:

1. Try running:
   test=pvlib.spectrum.mismatch.spectral_factor_pvspec(airmass_absolute = 1.5, clearsky_index = 1, module_type='fs4-1')
   or
   test=pvlib.spectrum.mismatch.spectral_factor_pvspec(airmass_absolute = 1.5, clearsky_index = 1, module_type='fs4-2')

In both cases you should get an error. For example:
Traceback (most recent call last):
File "", line 1, in
File "C:\Users\spelland.venv\spectral_env\Lib\site-packages\pvlib\spectrum\mismatch.py", line 585, in spectral_factor_pvspec
coefficients = _coefficients[module_type.lower()]
~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
KeyError: 'fs4-1'

2. If you run with one of the other module types, there should be no error. e.g: test_that_works =pvlib.spectrum.mismatch.spectral_factor_pvspec(airmass_absolute = 1.5, clearsky_index = 1, module_type='monosi')

[cwhanse]

Confirmed, thanks @sophie-pelland