doc/clone: Pick more compelling paths for the --reference example

doc/clone: Pick more compelling paths for the --reference example

There may be times when using one of your local repositories as a
reference for a new clone make sense, but the implied version-bump in
the old example isn't one of them.  I think a more intuitive example
is multi-user system with a central reference clone, and the new paths
hint at this use case.

Signed-off-by: W. Trevor King <redacted>
Signed-off-by: Junio C Hamano <redacted>