MM-11008: Fix translation and change the code to be auto-extracted (#9009)

i18n/en.json

@@ -99,6 +99,14 @@
     "id": "api.channel.add_user_to_channel.type.app_error",
     "translation": "Can not add user to this channel type"
   },
+  {
+    "id": "api.channel.change_channel_privacy.private_to_public",
+    "translation": "This channel has been converted to a Public Channel and can be joined by any team member."
+  },
+  {
+    "id": "api.channel.change_channel_privacy.public_to_private",
+    "translation": "This channel has been converted to a Private Channel."
+  },
   {
     "id": "api.channel.convert_channel_to_private.default_channel_error",
     "translation": "This default channel cannot be converted into a private channel."