evolve: remove a check which is already done by rewriteutil.precheck()
We have tests to check if fold is being performed on public cset.
There is no changes in test files because testing that never touched
the part this patch removes, and already caught in rewriteutil.precheck()
$ 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]