Bump pymongo from 4.15.2 to 4.15.3

Bumps [pymongo](https://github.com/mongodb/mongo-python-driver) from 4.15.2 to 4.15.3.
- [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@4.15.2...4.15.3)

---
updated-dependencies:
- dependency-name: pymongo
  dependency-version: 4.15.3
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -1,2 +1,2 @@
 dnspython==2.6.1
-pymongo==4.15.2
+pymongo==4.15.3