Use a stable link for the list of versions

Author: eregon

README.md

@@ -4,8 +4,8 @@ This action downloads a prebuilt ruby and adds it to `$PATH`.
 
 It currently supports the latest stable versions of MRI, JRuby and TruffleRuby.
 
-See https://github.com/eregon/ruby-install-builder/releases/latest for the
-available Ruby versions.
+See https://github.com/eregon/ruby-install-builder/blob/metadata/versions.json
+for the available Ruby versions.
 
 The action works for the `ubuntu-16.04`, `ubuntu-18.04` and `macos-latest` GitHub-hosted runners.  
 `windows-latest` is not yet supported.