watch: use manual pretty option

I tried dropping it in cec95bc1, but
unfortunately until we tag a release we'll have to manually update the
watch file.

watch

 version=4
-opts="mode=git, pgpmode=none" \
+opts="mode=git, pgpmode=none, pretty=0.0.3+git%cd.%h" \
 https://github.com/pistacheio/pistache.git \
 HEAD debian uupdate