Restore `$val` in `WP_Importer::bump_request_timeout()` - even though the parent class and `WP_Import` ignore the parameter, it creates an incompatible interface notice in the plugin.

See [28629].



git-svn-id: https://develop.svn.wordpress.org/trunk@28637 602fd350-edb4-49c9-b593-d223f7449a82