4606. [port] Stop using experimental "Experimental keys on scalar"

feature of perl as it has been removed. [RT #45012]

(cherry picked from commit a14562e120)

bin/tests/system/statschannel/server-xml.pl

@@ -14,7 +14,7 @@ use XML::Simple;
 my $ref = XMLin("xml.stats");
 my $counters = $ref->{server}->{counters};
 foreach $group (@$counters) {
-    foreach $key (keys $group->{counter}) {
+    foreach $key (keys %{$group->{counter}}) {
         print $group->{type} . " " . $key . ": ". $group->{counter}->{$key}->{content} . "\n";
     }
 }