Remove last usage of ujson

synapse/python_dependencies.py

@@ -34,7 +34,6 @@ REQUIREMENTS = {
     "bcrypt": ["bcrypt>=3.1.0"],
     "pillow": ["PIL"],
     "pydenticon": ["pydenticon"],
-    "ujson": ["ujson"],
     "blist": ["blist"],
     "pysaml2>=3.0.0": ["saml2>=3.0.0"],
     "pymacaroons-pynacl": ["pymacaroons"],

synapse/storage/group_server.py

@@ -19,7 +19,7 @@ from synapse.api.errors import SynapseError
 
 from ._base import SQLBaseStore
 
-import ujson as json
+import simplejson as json
 
 
 # The category ID for the "default" category. We don't store as null in the