Bump pymongo from 4.15.3 to 4.15.4 in /reference-apps/fastapi-api-first (#17)

Bumps [pymongo](https://github.com/mongodb/mongo-python-driver) from 4.15.3 to 4.15.4.
- [Release notes](https://github.com/mongodb/mongo-python-driver/releases)
- [Changelog](https://github.com/mongodb/mongo-python-driver/blob/master/doc/changelog.rst)
- [Commits](mongodb/mongo-python-driver@4.15.3...4.15.4)

---
updated-dependencies:
- dependency-name: pymongo
  dependency-version: 4.15.4
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

reference-apps/fastapi-api-first/requirements.txt

@@ -16,7 +16,7 @@ asyncpg==0.30.0
 aiomysql==0.3.2
 cryptography>=41.0.0  # Required for MySQL caching_sha2_password auth
 motor==3.7.1
-pymongo==4.15.3
+pymongo==4.15.4
 
 # Redis and Caching
 redis[hiredis]==7.0.1  # Compatible with fastapi-cache2 (requires <5.0.0)