Declare version 4 in d/watch

debian/watch

-version=3
+version=4
 opts=filenamemangle=s#.*/([\d.]+\.tar\.[gx]z)#ibus-m17n-$1# \
 https://github.com/ibus/ibus-m17n/releases \
 .*/([\d.]+)\.tar\.[gx]z debian uupdate