REGTEST: make map_regm_with_backref require 1.7

map_regm was only introduced in 1.7, I don't know why the require field
was set to 1.6, probably tha the test evolved and didn't start with
map_regm.
diff --git a/reg-tests/http-rules/map_regm_with_backref.vtc b/reg-tests/http-rules/map_regm_with_backref.vtc
index 4937269..790a10b 100644
--- a/reg-tests/http-rules/map_regm_with_backref.vtc
+++ b/reg-tests/http-rules/map_regm_with_backref.vtc
@@ -10,7 +10,7 @@
 varnishtest "map_regm get_trash_chunk test"
 feature ignore_unknown_macro
 
-#REQUIRE_VERSION=1.6
+#REQUIRE_VERSION=1.7
 #REGTEST_TYPE=bug
 
 syslog S1 -level notice {