const runtime.traceEvSpanFree

2 uses

	runtime (current package)
		traceallocfree.go#L102: 	tl.eventWriter(traceGoRunning, traceProcRunning).commit(traceEvSpanFree, traceSpanID(s))
		traceexp.go#L57: 	traceEvSpanFree  // heap span free [timestamp, id]