services.cgi: avoid experimental warnings

- add single line to code: no warnings 'experimental';
- corrects this issue:
    https://lists.ipfire.org/pipermail/development/2022-December/015113.html

Signed-off-by: Jon Murphy <jon.murphy@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

html/cgi-bin/services.cgi

@@ -21,6 +21,7 @@
 
 use strict;
 use feature "switch";
+no warnings 'experimental';
 # enable only the following on debugging purpose
 #use warnings;
 #use CGI::Carp 'fatalsToBrowser';