revert debian/watch version to 3 for compatibility with jh_repack

debian/watch

-version=4
+version=3
 opts=uversionmangle=s/(\d)[_\.\-\+]?((RC|rc|pre|dev|beta|alpha|b|a)[\-\.]?\d*)$/$1~$2/,pgpsigurlmangle=s/$/.asc/ \
 https://www.apache.org/dist/xmlgraphics/commons/source/xmlgraphics-commons-(\d.*)-src\.(?:tgz|tbz2|txz|tar\.(?:gz|bz2|xz)) debian jh_repack