chore(buildpacks): update heroku-buildpack-go to v64

See heroku/heroku-buildpack-go@v62...v64

Author: mboersma

rootfs/builder/install-buildpacks

@@ -30,7 +30,7 @@ mkdir -p $BUILDPACK_INSTALL_PATH
 
 download_buildpack https://github.com/heroku/heroku-buildpack-multi.git          v1.0.0   01-multi
 download_buildpack https://github.com/heroku/heroku-buildpack-clojure.git        v76      02-clojure
-download_buildpack https://github.com/heroku/heroku-buildpack-go.git             v62      03-go
+download_buildpack https://github.com/heroku/heroku-buildpack-go.git             v64      03-go
 download_buildpack https://github.com/heroku/heroku-buildpack-gradle.git         v21      04-gradle
 download_buildpack https://github.com/heroku/heroku-buildpack-grails.git         v21      05-grails
 download_buildpack https://github.com/heroku/heroku-buildpack-java.git           v51      06-java