Improve error messages when DeepL quota is exceeded (#26704)

config/locales/en.yml

@@ -1709,6 +1709,10 @@ en:
       default: "%b %d, %Y, %H:%M"
       month: "%b %Y"
       time: "%H:%M"
+  translation:
+    errors:
+      quota_exceeded: The server-wide usage quota for the translation service has been exceeded.
+      too_many_requests: There have been too many requests to the translation service recently.
   two_factor_authentication:
     add: Add
     disable: Disable 2FA