api/instance/translator_languages: only query service if enabled

The instance controller already had code for an {:enabled, false}
return, just nothing actually checked or produced this value.

This was especially noticeable when using mastodon-fe and not having a
valid API token for the default DeepL service configured. Mastodon-fe
proactively queries this endpoint and upon receiving a 403 response
the controller raised an exception leading to this exception and
call trace being spammed in logs.

CHANGELOG.md

@@ -42,6 +42,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - fixed potential data inconsistencies and API ordering for rediscovered partially pruned objects
 - fixed tagged (mentioned) but not addressed users receiving notifications about
     statuses they are not actually allowed to access
+- fixed tranlator service being queried for supported languages even if not enabled
 
 ### Changed
 - New installations (not existing instances) now default to the `simple` full-text-search config

lib/pleroma/akkoma/translator.ex

@@ -5,9 +5,11 @@ defmodule Pleroma.Akkoma.Translator do
     module = Pleroma.Config.get([:translator, :module])
 
     @cachex.fetch!(:translations_cache, "languages:#{module}}", fn _ ->
-      with {:ok, source_languages, dest_languages} <- module.languages() do
+      with {_, true} <- {:enabled, Pleroma.Config.get([:translator, :enabled])},
+           {:ok, source_languages, dest_languages} <- module.languages() do
         {:commit, {:ok, source_languages, dest_languages}}
       else
+        {:enabled, _} -> {:commit, {:enabled, false}}
         {:error, err} -> {:ignore, {:error, err}}
       end
     end)