REGTESTS: Remove REQUIRE_VERSION=1.5 from all tests

HAProxy 1.5 is EOL, thus this always matches.

1.6 / 1.7 were already removed in:
d8be0018fe85b5f815d59cdf1e0400274a99a9b1 (1.6)
1b095cac9468d0c3eeb157e9b1a2947487bd3c83 (1.7)
diff --git a/reg-tests/ssl/ssl_frontend_samples.vtc b/reg-tests/ssl/ssl_frontend_samples.vtc
index 86851cf..bca0856 100644
--- a/reg-tests/ssl/ssl_frontend_samples.vtc
+++ b/reg-tests/ssl/ssl_frontend_samples.vtc
@@ -1,7 +1,6 @@
 #REGTEST_TYPE=devel
 
 varnishtest "Test the ssl_f_* sample fetches"
-#REQUIRE_VERSION=1.5
 #REQUIRE_OPTIONS=OPENSSL
 feature ignore_unknown_macro