User's Guide: Update instructions for generating crop maturity reqts

### What sort(s) of documentation issue is this?
- [ ] Something is missing.
- [x] Something is (or might be) incorrect or outdated.
- [ ] Something is confusing.
- [ ] Something is broken.

### What part(s) of the documentation does this concern?
- [ ] [Technical Note](https://escomp.github.io/CTSM/tech_note/index.html) (science and design of the model)
- [x] [User's Guide](https://escomp.github.io/CTSM/users_guide/index.html) (using the model and related tools)
- [ ] Somewhere else (e.g., README file, tool help text, or code comment): _Please specify_
- [ ] I don't know

### Describe the issue
The [instructions for generating crop maturity requirements](https://escomp.github.io/CTSM/users_guide/running-special-cases/Running-with-custom-crop-calendars.html#generating-maturity-requirements) need some additional lines in `user_nl_clm`:
```
model_year_align_cropcal_swindows = YEAR
stream_fldFileName_cultivar_gdds = ''
stream_fldFileName_gdd20_baseline = ''
cropcals_rx_adapt = .false.
cropcals_rx = .true.
```

Also, consider adding instructions for custom surface dataset with all crops everywhere:
```
fsurdat = '/glade/work/samrabin/fsurdat_all_crops_everywhere/surfdata_360x720cru_hist_78pfts_CMIP6_simyr1850_c230201.all_crops_everywhere.netCDF-3.nc'
do_transient_crops = .false.
flanduse_timeseries = ''
use_init_interp = .true.
```