tests/narrow-library.sh

graft: don't remove from a list in a loop

This addresses a TODO added in a1381eea7c7d (graft: do not use
`.remove` on a smart set (regression), 2014-04-28). I couldn't measure
any speedup.

Differential Revision: https://phab.mercurial-scm.org/D7805

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