Fix srctype docs

[hbushouse]

This PR fixes the docs for the calwebb_spec2 pipeline and the srctype step to indicate that srctype is applied to WFSS exposures (error in docs pointed out by an INS user on Slack).

Checklist for maintainers

• added entry in CHANGES.rst within the relevant release section
• updated or added relevant tests
• updated relevant documentation
• added relevant milestone
• added relevant label(s)
• ran regression tests, post a link to the Jenkins job below.
  How to run regression tests on a PR
• Make sure the JIRA ticket is resolved properly

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (6b12a2a) 77.53% compared to head (e814dad) 77.53%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7536   +/-   ##
=======================================
  Coverage   77.53%   77.53%           
=======================================
  Files         452      452           
  Lines       36200    36200           
=======================================
  Hits        28066    28066           
  Misses       8134     8134           

Flag	Coverage Δ		*Carryforward flag
nightly	77.53% <ø> (ø)		Carriedforward from 6b12a2a

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