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].


Built from https://develop.svn.wordpress.org/trunk@28637


git-svn-id: http://core.svn.wordpress.org/trunk@28455 1a063a9b-81f0-0310-95a4-ce76da25c4cd