feat: add missing index for jwk table

[aeneasr]

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
  security@ory.sh) 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

All modified and coverable lines are covered by tests ✅

Comparison is base (8e94929) 76.11% compared to head (d7859f2) 75.96%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3691      +/-   ##
==========================================
- Coverage   76.11%   75.96%   -0.15%     
==========================================
  Files         134      134              
  Lines       11764    10065    -1699     
==========================================
- Hits         8954     7646    -1308     
+ Misses       2238     1906     -332     
+ Partials      572      513      -59     

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