Bump pymongo from 3.11.3 to 3.11.4 in /emmet-core

Bumps [pymongo](https://github.com/mongodb/mongo-python-driver) from 3.11.3 to 3.11.4.
- [Release notes](https://github.com/mongodb/mongo-python-driver/releases)
- [Changelog](https://github.com/mongodb/mongo-python-driver/blob/3.11.4/doc/changelog.rst)
- [Commits](mongodb/mongo-python-driver@3.11.3...3.11.4)

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

emmet-core/requirements.txt

@@ -3,5 +3,5 @@ monty==v2021.3.3
 pydantic==1.8.1
 pybtex==0.24.0
 typing-extensions==3.7.4.3
-pymongo==3.11.3
+pymongo==3.11.4
 maggma==0.26.0