fix: proxyIP can't be a subnet

Co-authored-by: Stéphane Lesimple <speed47_github@speed47.net>

lib/perl/OVH/Bastion/Plugin/ACL.pm

@@ -92,7 +92,7 @@ sub check {
         }
 
         # validate proxy host format (same as regular host validation)
-        if ($proxyIp !~ m{^[a-zA-Z0-9._/:-]+$}) {
+        if ($proxyIp !~ m{^[a-zA-Z0-9._:-]+$}) {
             return R('ERR_INVALID_PARAMETER', msg => "Proxy host name '$proxyIp' seems invalid");
         }