fix: accept login_challenge in SPA verification flows

[jonas-jonas]

Related issue(s)

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got the approval (please contact
  [email protected]) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

[codecov]

Codecov Report

Attention: Patch coverage is 81.25000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 78.59%. Comparing base (07cb83c) to head (cde17c4).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
selfservice/flow/verification/handler.go	81.25%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4284      +/-   ##
==========================================
- Coverage   78.59%   78.59%   -0.01%     
==========================================
  Files         381      381              
  Lines       27370    27382      +12     
==========================================
+ Hits        21512    21521       +9     
- Misses       4236     4238       +2     
- Partials     1622     1623       +1     

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