Fix unintentionally inverted boolean

Fixes a problem introduced by da6edc9cba.

Related to #145 (Github Pull Request).

roles/matrix-synapse/defaults/main.yml

@@ -150,7 +150,7 @@ matrix_synapse_password_config_pepper: ""
 # Controls if Synapse allows people to authenticate against its local database.
 # It may be useful to disable this if you've configured additional password providers
 # and only wish authentication to happen through them.
-matrix_synapse_password_config_localdb_enabled: false
+matrix_synapse_password_config_localdb_enabled: true
 
 # Controls the number of events that Synapse caches in memory.
 matrix_synapse_event_cache_size: "100K"