fix: OIDC provider field in spec

[provokateurin]

Related issue(s)

Fixes #1739 for now

Checklist

• I have read the contributing guidelines.
• 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 green light (please contact
  security@ory.sh) from the maintainers to push
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• I have added tests that prove my fix is effective or that my feature
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[provokateurin]

Test failure seems unrelated to the changes.

[codecov]

Codecov Report

Merging #1809 (01996f0) into master (c6aa6b5) will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1809      +/-   ##
==========================================
+ Coverage   74.07%   74.13%   +0.05%     
==========================================
  Files         260      260              
  Lines       12770    12770              
==========================================
+ Hits         9460     9467       +7     
+ Misses       2680     2673       -7     
  Partials      630      630              

Impacted Files	Coverage Δ
selfservice/strategy/oidc/strategy_login.go	63.33% <ø> (ø)
selfservice/strategy/oidc/strategy_registration.go	54.34% <ø> (ø)
cmd/courier/watch.go	72.41% <0.00%> (+12.06%)	⬆️

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