Fix typo.

i18n/en.i18n.json

@@ -724,5 +724,5 @@
   "act-duenow": "was reminding the current due (__timeValue__) of __card__ is now",
   "act-atUserComment": "You were mentioned in [__board__] __card__",
   "delete-user-confirm-popup": "Are you sure you want to delete this account? There is no undo.",
-  "accounts-allowUserDelete": "Allow users to self deleting their account"
+  "accounts-allowUserDelete": "Allow users to self delete their account"
 }