Geo: Fix incorrect datetime_with_timezone schema

The migration used datetime_with_timezone, but the schema used datetime.

ee/db/geo/schema.rb

@@ -75,7 +75,7 @@ ActiveRecord::Schema.define(version: 20180427114641) do
     t.boolean "repository_checksum_mismatch", default: false, null: false
     t.boolean "wiki_checksum_mismatch", default: false, null: false
     t.boolean "last_repository_check_failed"
-    t.datetime "last_repository_check_at"
+    t.datetime_with_timezone "last_repository_check_at"
   end
 
   add_index "project_registry", ["last_repository_successful_sync_at"], name: "index_project_registry_on_last_repository_successful_sync_at", using: :btree