Fix matrix_synapse_ext_password_provider_ldap_start_tls (it's boolean)

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

@@ -977,7 +977,7 @@ password_providers:
     config:
       enabled: true
       uri: {{ matrix_synapse_ext_password_provider_ldap_uri|string|to_json }}
-      start_tls: {{ matrix_synapse_ext_password_provider_ldap_start_tls|string|to_json }}
+      start_tls: {{ matrix_synapse_ext_password_provider_ldap_start_tls|to_json }}
       base: {{ matrix_synapse_ext_password_provider_ldap_base|string|to_json }}
       attributes:
         uid: {{ matrix_synapse_ext_password_provider_ldap_attributes_uid|string|to_json }}