fix: accept OIDC login request in browser+JSON login flow

[hperl]

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

Merging #3271 (1b09509) into master (22e8daf) will decrease coverage by 0.01%.
The diff coverage is 94.11%.

❗ Current head 1b09509 differs from pull request most recent head a44dfca. Consider uploading reports for the commit a44dfca to get more accurate results

@@            Coverage Diff             @@
##           master    #3271      +/-   ##
==========================================
- Coverage   78.13%   78.12%   -0.01%     
==========================================
  Files         325      325              
  Lines       21102    21079      -23     
==========================================
- Hits        16487    16468      -19     
+ Misses       3387     3383       -4     
  Partials     1228     1228              

Impacted Files	Coverage Δ
hydra/fake.go	70.00% <88.88%> (+25.55%)	⬆️
selfservice/flow/login/hook.go	86.23% <100.00%> (+0.62%)	⬆️
selfservice/strategy/oidc/strategy_login.go	67.05% <100.00%> (ø)

... and 1 file with indirect coverage changes