Fix clang 20 shadows variable in global scope warning

Fix clang 20 shadows variable in global scope warning

Fixes:

 [4822/4916] Compiling source3/torture/torture.c
 ../../source3/torture/torture.c:685:6: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
  685 |         int timezone = smb1cli_conn_server_time_zone(cli->conn);
      |             ^
 /usr/include/time.h:234:17: note: previous declaration is here
  234 | extern long int timezone;
      |                 ^
 1 error generated.

Signed-off-by: Gary Lockyer <gary@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Anoop C S <anoopcs@samba.org>