REGTEST: make the "set ssl cert" require version 2.1

This test fails on 2.0 and earlier since the feature was introduced in 2.1,
let's add the REQUIRE_VERSION tag.

reg-tests/ssl/set_ssl_cert.vtc

@@ -8,6 +8,7 @@
 # - Check that the curl -v option still return the SSL CN
 
 varnishtest "Test the 'set ssl cert' feature of the CLI"
+#REQUIRE_VERSION=2.1
 #REQUIRE_OPTIONS=OPENSSL
 #REQUIRE_BINARIES=socat,curl
 feature ignore_unknown_macro