Add "SCHEMA" to the query in configure_connection like as other adapters

This makes to be able to ignore the query in `assert_queries` even if
accidentally reconnected a connection.

https://buildkite.com/rails/rails/builds/61917#4c49187a-3173-4d5c-8a8d-d65768f5bfc9/1000-1799

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -737,7 +737,7 @@ module ActiveRecord
           end.compact.join(", ")
 
           # ...and send them all in one query
-          execute "SET #{encoding} #{sql_mode_assignment} #{variable_assignments}"
+          execute("SET #{encoding} #{sql_mode_assignment} #{variable_assignments}", "SCHEMA")
         end
 
         def column_definitions(table_name) # :nodoc: