[MM-27535] Change string to be more in-line with designs and the front end verbiage (#15320)

* Change string to be more in-line with designs and the front end verbiage

* Tweak tests to have the new string

* fix eetests

i18n/en.json

@@ -2224,7 +2224,7 @@
   },
   {
     "id": "api.team.invite_members.limit_reached.app_error",
-    "translation": "You've reached the user limit of your current tier"
+    "translation": "You've reached the free tier user limit"
   },
   {
     "id": "api.team.invite_members.no_one.app_error",