Remove unused virtualenv dependency (#89)

We shouldn't need to require the virtualenv dependency after this change
to use venv instead:
ConsultingMD/image-builder#221

This PR removes the `depends_on` for `virtualenv`.

formula/ih-core.rb

@@ -15,7 +15,6 @@ class IhCore < Formula
   depends_on "jq"
   depends_on "yq"
   depends_on "go-jira"
-  depends_on "virtualenv"
   depends_on "envconsul"
   depends_on "openssl@3"
   depends_on "coreutils"