[PM-20225] Prevent legacy users without userkey from logging in (#14267)

* Prevent legacy users without userkey from logging in

* Remove further web-migration code for legacy users

* Add i18n for legacy user error message

* Update comment

* Remove migrate legacy component

* Remove i18n messages

* Remove migrate legacy encryption reference

apps/browser/src/_locales/en/messages.json

@@ -1365,8 +1365,8 @@
   "featureUnavailable": {
     "message": "Feature unavailable"
   },
-  "encryptionKeyMigrationRequired": {
-    "message": "Encryption key migration required. Please login through the web vault to update your encryption key."
+  "legacyEncryptionUnsupported": {
+    "message": "Legacy encryption is no longer supported. Please contact support to recover your account."
   },
   "premiumMembership": {
     "message": "Premium membership"