Fix deprecation: insert_sql is deprecated and will be removed

changelogs/unreleased/deprecated-insert-sql.yml

+---
+title: 'Fix deprecation: insert_sql is deprecated and will be removed'
+merge_request: 23944
+author: Jasper Maes
+type: other

db/migrate/20180413022611_create_missing_namespace_for_internal_users.rb

@@ -46,7 +46,7 @@ class CreateMissingNamespaceForInternalUsers < ActiveRecord::Migration[4.2]
     end
 
     insert_query = "INSERT INTO namespaces(owner_id, path, name, created_at, updated_at) VALUES(#{user_id}, '#{path}', '#{path}', NOW(), NOW())"
-    namespace_id = connection.insert_sql(insert_query)
+    namespace_id = connection.insert(insert_query)
 
     create_route(namespace_id)
   end