makefile: remove Ubuntu Yakkety and Zesty docker targets
Yakkety (16.10) was supported until 2017-07-20 and Zesty (17.04) was supported
until 2018-01-13.
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state