d/watch: Switch to format version 4.

debian/watch

-version=3
+version=4
 opts="uversionmangle=s/(alpha|beta|rc)/~$1/i,dversionmangle=s/\+debian\d$//" \
 https://pear.horde.org/ https://pear.horde.org/get/Horde_JavascriptMinify_Jsmin-(.+)\.tgz