matrix: rebase config against upstream

roles/matrix/templates/matrix-synapse/log.yaml.j2

@@ -69,9 +69,7 @@ root:
     # Write logs to the `buffer` handler, which will buffer them together in memory,
     # then write them to a file.
     #
-    # Replace "buffer" with "console" to log to stderr instead. (Note that you'll
-    # also need to update the configuration for the `twisted` logger above, in
-    # this case.)
+    # Replace "buffer" with "console" to log to stderr instead.
     #
     handlers: [buffer]