[fix] /preferences: remove the empty engine category "social medias" (it is "social media")

searx/settings_defaults.py

@@ -30,7 +30,7 @@ CATEGORY_ORDER = [
     'it',
     'science',
     'files',
-    'social medias',
+    'social media',
 ]
 STR_TO_BOOL = {
     '0': False,