Remove /heap endpoint (#4460)
Remove /heap endpoint (#4460)

It was added 5 years ago by Matt and I'm not sure anyone ever used
it after public release (since we have /debug/pprof/heap as well).

It also lacked error checking and allows people to write to disk over HTTP.

Signed-off-by: Julius Volz <d7748b1e6f41fd74500c5ccae0980eab88c2ef61@gmail.com>
keegancsmith/prometheus,prometheus/prometheus,Gouthamve/prometheus,GoogleCloudPlatform/prometheus,kangwoo/prometheus,prometheus/prometheus,alileza/prometheus,alileza/prometheus,kangwoo/prometheus,alileza/prometheus,alileza/prometheus,prometheus/prometheus,GoogleCloudPlatform/prometheus,keegancsmith/prometheus,kangwoo/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,prometheus/prometheus,prometheus/prometheus,keegancsmith/prometheus,Gouthamve/prometheus,kangwoo/prometheus,alileza/prometheus,Gouthamve/prometheus,keegancsmith/prometheus,Gouthamve/prometheus,GoogleCloudPlatform/prometheus,GoogleCloudPlatform/prometheus