Remove WP version everywhere by Frisno removes WordPress version from RSS, posts and pages supports network activation.
A simple plugin to prevent people from knowing what version of WordPress you’re using via your HTML source or RSS feed.
Unlike other plugins that just remove the version from WordPress generator tag on pages, this plugin simply tells the automatic function to not print out anything, not even on RSS Feeds.
Download and info: http://wordpress.org/extend/plugins/remove-wp-version-everywhere/