[NDR-323] Fix env var reference

Author: megan-bower4

lambdas/tests/e2e/helpers/lloyd_george_mockcis2_helper.py

@@ -11,7 +11,7 @@
 
 class LloydGeorgeMockcis2Helper:
     def __init__(self, ods, repository_role):
-        self.mock_key = API_KEY
+        self.mock_key = os.environ.get("MOCK_CIS2_KEY") or ""
         self.api_endpoint = data_helper.api_endpoint
         self.ods = ods
         self.repository_role = repository_role