refactor: avoid operator precedence bugs

lib-ee/emqx_ee_bridge/src/emqx_ee_bridge_mysql.erl

@@ -95,7 +95,8 @@ fields("config") ->
                 }
             )}
     ] ++
-        emqx_connector_mysql:fields(config) -- emqx_connector_schema_lib:prepare_statement_fields();
+        (emqx_connector_mysql:fields(config) --
+            emqx_connector_schema_lib:prepare_statement_fields());
 fields("creation_opts") ->
     Opts = emqx_resource_schema:fields("creation_opts"),
     [O || {Field, _} = O <- Opts, not is_hidden_opts(Field)];

lib-ee/emqx_ee_bridge/src/emqx_ee_bridge_pgsql.erl

@@ -97,7 +97,8 @@ fields("config") ->
                 }
             )}
     ] ++
-        emqx_connector_pgsql:fields(config) -- emqx_connector_schema_lib:prepare_statement_fields();
+        (emqx_connector_pgsql:fields(config) --
+            emqx_connector_schema_lib:prepare_statement_fields());
 fields("creation_opts") ->
     Opts = emqx_resource_schema:fields("creation_opts"),
     [O || {Field, _} = O <- Opts, not is_hidden_opts(Field)];