Bump pymongo in /eng/scripts/openapitools/python/cacherepostructure (#8032)

Bumps [pymongo](https://github.com/mongodb/mongo-python-driver) from 3.13.0 to 4.6.3.
- [Release notes](https://github.com/mongodb/mongo-python-driver/releases)
- [Changelog](https://github.com/mongodb/mongo-python-driver/blob/master/doc/changelog.rst)
- [Commits](https://github.com/mongodb/mongo-python-driver/compare/3.13.0...4.6.3)

---
updated-dependencies:
- dependency-name: pymongo
  dependency-type: direct:production
...

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eng/scripts/openapitools/python/cacherepostructure/requirements.txt

@@ -1,2 +1,2 @@
 GitPython==3.1.41
-pymongo==3.13.0
+pymongo==4.6.3