README: link to latest release

This will automatically redirect to the release marked "latest" in GitHub.
So the link won't become stale and doesn't need updating.

Signed-off-by: Stephan Renatus <stephan@styra.com>

README.md

@@ -122,7 +122,7 @@ strings.
 Precompiled binaries for several platforms are available for download
 at:
 
-**https://github.com/mthom/scryer-prolog/releases/tag/v0.9.3**
+**https://github.com/mthom/scryer-prolog/releases/latest**
 
 ### Native Compilation