tests: remove a"| head -n 2" that just hides an error code
The output from core used to be longer and it made sense, but no
longer does.
CORE-TEST-OUTPUT-UPDATE: 5199c5b6fd29
$ cat >> $HGRCPATH <<EOF
> [ui]
> logtemplate={rev}:{node|short}[{bookmarks}] ({obsolete}/{phase}) {desc|firstline}\n
> [extensions]
> EOF
$ echo "evolve=$(echo $(dirname $TESTDIR))/hgext3rd/evolve/" >> $HGRCPATH
$ mkcommit() {
> echo "$1" > "$1"
> hg add "$1"
> hg ci -m "add $1"
> }
$ hg init repo
$ cd repo
$ mkcommit a
$ mkcommit b
test disabling commands
$ cat >> .hg/hgrc <<EOF
> [experimental]
> evolution=createmarkers
> allowunstable
> exchange
> EOF
$ hg prune
hg: unknown command 'prune'
(use 'hg help' for a list of commands)
[255]