tests/narrow-library.sh

narrow: drop obsolete support for old Mercurial

Not needed since narrow is shipped with core.

Differential Revision: https://phab.mercurial-scm.org/D5397

cat >> $HGRCPATH <<EOF
[extensions]
narrow=
[ui]
ssh=python "$TESTDIR/dummyssh"
[experimental]
changegroup3 = True
EOF