Fixed updating the plugin translation catalog

Ignore the plugins folder for FlaskBB's translations.

babel.cfg

@@ -1,3 +1,4 @@
+[ignore: **/plugins/**]
 [python: **.py]
 [jinja2: **/templates/**.html]
 extensions=jinja2.ext.autoescape,jinja2.ext.with_

manage.py

@@ -255,7 +255,7 @@ def update_plugin_translations(plugin):
     subprocess.call(["pybabel", "extract", "-F", "babel.cfg",
                      "-k", "lazy_gettext", "-o", "messages.pot",
                      plugin_folder])
-    subprocess.call(["pybabel", "update", "-i", "messages.pot"
+    subprocess.call(["pybabel", "update", "-i", "messages.pot",
                      "-d", translations_folder])
     os.unlink("messages.pot")