Fix syntax error in example batch script

doc/phpsdk_pgo_prep_elevated.bat.example

@@ -18,7 +18,7 @@ rem netsh advfirewall set allprofiles state off
 
 rem NGINX
 netsh advfirewall firewall add rule name="NGINX for PGO" dir=in action=allow program="C:\php-snap-build\php-sdk\pgo\work\server\nginx\nginx.exe" profile=private
-for \l %%p in (8081, 1, 8091) do (
+for /l %%p in (8081, 1, 8091) do (
 	netsh advfirewall firewall add rule name="Open Port %%p for PHP PGO" dir=in action=allow protocol=TCP localport=%%p profile=private
 	netsh advfirewall firewall add rule name="Open Port %%p for PHP PGO" dir=in action=allow protocol=UDP localport=%%p profile=private
 )