DOC: management: rename show stats domain cli "dns" to "resolvers"

In commit f8642ee ("MEDIUM: resolvers: rename dns extra counters to
resolvers extra counters"), we renamed "dns" counters to "resolvers", but
we forgot to update the documentation accordingly.

This may be backported to all stable versions.

(cherry picked from commit cf913c2)
Signed-off-by: Christopher Faulet <[email protected]>

Author: Darlelet

doc/management.txt

@@ -3264,8 +3264,8 @@ show sess <id> | older <age> | susp | all
   is meant to be interpreted while checking function strm_dump_to_buffer() in
   src/stream.c to figure the exact meaning of certain fields.
 
-show stat [domain <dns|proxy>] [{<iid>|<proxy>} <type> <sid>] [typed|json] \
-          [desc] [up|no-maint]
+show stat [domain <resolvers|proxy>] [{<iid>|<proxy>} <type> <sid>] \
+          [typed|json] [desc] [up|no-maint]
   Dump statistics. The domain is used to select which statistics to print; dns
   and proxy are available for now. By default, the CSV format is used; you can
   activate the extended typed output format described in the section above if