REGTEST: fix haproxy required version for server removal test

The ability to delete all servers is introduced in 2.5 release.
diff --git a/reg-tests/server/cli_delete_server.vtc b/reg-tests/server/cli_delete_server.vtc
index 7487fc7..bfa9ff4 100644
--- a/reg-tests/server/cli_delete_server.vtc
+++ b/reg-tests/server/cli_delete_server.vtc
@@ -5,7 +5,7 @@
 
 feature ignore_unknown_macro
 
-#REQUIRE_VERSION=2.4
+#REQUIRE_VERSION=2.5
 
 haproxy h1 -conf {
 	defaults