REGTESTS: Remove REQUIRE_VERSION=1.7 from all tests

HAProxy 1.7 is the lowest supported version, thus this always matches.
diff --git a/reg-tests/http-rules/map_regm_with_backref.vtc b/reg-tests/http-rules/map_regm_with_backref.vtc
index 7a5b879..78af447 100644
--- a/reg-tests/http-rules/map_regm_with_backref.vtc
+++ b/reg-tests/http-rules/map_regm_with_backref.vtc
@@ -10,7 +10,6 @@
 varnishtest "map_regm get_trash_chunk test"
 feature ignore_unknown_macro
 
-#REQUIRE_VERSION=1.7
 #REGTEST_TYPE=bug
 
 syslog S1 -level notice {