Fix a typo when comparing the URI & method during UI Auth. (#7689)

changelog.d/7689.bugfix

@@ -0,0 +1 @@
+Compare the URI and method during user interactive authentication (instead of the URI twice). Bug introduced in 1.13.0rc1.

synapse/handlers/auth.py

@@ -297,7 +297,7 @@ class AuthHandler(BaseHandler):
 
         # Convert the URI and method to strings.
         uri = request.uri.decode("utf-8")
-        method = request.uri.decode("utf-8")
+        method = request.method.decode("utf-8")
 
         # If there's no session ID, create a new session.
         if not sid: