bundle: do no check the changegroup version if no changegroup is included
We don't need to check the compatibility of something we will not use.
In practice this was getting in the was of `streamv2` bundles on a narrow
repository as the 'cg.version=02' value was rejected by this checks.
$ cat >> $HGRCPATH <<EOF
> [censor]
> policy=ignore
> EOF
$ mkdir r
$ cd r
$ hg init
$ echo secret > target
$ hg commit -Am "secret"
adding target
$ touch bystander
$ hg commit -Am "innocent"
adding bystander
$ echo erased-secret > target
$ hg commit -m "erased secret"
$ hg censor target --config extensions.censor= -r ".^^"
checking for the censored content in 1 heads
checking for the censored content in the working directory
censoring 1 file revisions
$ hg update ".^"
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cat target
$ hg update tip
1 files updated, 0 files merged, 0 files removed, 0 files unresolved