MINOR: http_act: mark normalize-uri as experimental

normalize-uri http rule is marked as experimental, so it cannot be
activated without the global 'expose-experimental-directives'. The
associated vtc is updated to be able to use it.
diff --git a/reg-tests/http-rules/normalize_uri.vtc b/reg-tests/http-rules/normalize_uri.vtc
index cc88060..47032d9 100644
--- a/reg-tests/http-rules/normalize_uri.vtc
+++ b/reg-tests/http-rules/normalize_uri.vtc
@@ -11,6 +11,9 @@
 } -repeat 63 -start
 
 haproxy h1 -conf {
+    global
+        expose-experimental-directives
+
     defaults
         mode http
         timeout connect 1s