type fix

Author: BJSS-russell-pollock

gateway-api/src/gateway_api/clinical_jwt/jwt.py

@@ -36,7 +36,7 @@ def exp_time(self) -> str:
     def encode(self) -> str:
         return pyjwt.encode(
             self.payload(),
-            key="None",
+            key=None,  # type: ignore
             algorithm=self.algorithm,
             headers={"typ": self.type},
         )