bash_completion: use correct command for listing shelves

Previously, _hg_shelves used the unshelve command to list current shelves. This
is actually the wrong command. The correct usage is 'hg shelve -l' so we use
that instead.

contrib/bash_completion

@@ -597,7 +597,7 b' complete -o bashdefault -o default -o no'
 # shelve
 _hg_shelves()
 {
-    local shelves="$(_hg_cmd unshelve -l .)"
+    local shelves="$(_hg_cmd shelve -ql)"
     local IFS=$'\n'
     COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$shelves' -- "$cur"))
 }