Bump serde_json from 1.0.116 to 1.0.149 in /cmd/pinniped-proxy

Bumps [serde_json](https://github.com/serde-rs/json) from 1.0.116 to 1.0.149.
- [Release notes](https://github.com/serde-rs/json/releases)
- [Commits](serde-rs/json@v1.0.116...v1.0.149)

---
updated-dependencies:
- dependency-name: serde_json
  dependency-version: 1.0.149
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]