fix: add missing indexes and remove unused index

[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

[aeneasr]

https://github.com/ory/kratos/actions/runs/7901340760/job/21804831147?pr=3756#step:14:5107

🙄

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (cfa3074) 78.05% compared to head (c85062b) 78.36%.
Report is 9 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3756      +/-   ##
==========================================
+ Coverage   78.05%   78.36%   +0.30%     
==========================================
  Files         355      347       -8     
  Lines       24836    23903     -933     
==========================================
- Hits        19386    18731     -655     
+ Misses       3962     3761     -201     
+ Partials     1488     1411      -77     

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