src: fix Systemtap node_gc_stop probe

The process("node").mark("gc__stop") is actually
process("node").mark("gc__done"). Use the proper name so that a
developer can use SystemTap to determine the duration of garbage
collection.

PR-URL: #20152
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Matheus Marchini <matheus@sthima.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>

src/node.stp

@@ -125,7 +125,7 @@ probe node_gc_start = process("node").mark("gc__start")
     flags);
 }
 
-probe node_gc_stop = process("node").mark("gc__stop")
+probe node_gc_stop = process("node").mark("gc__done")
 {
   scavenge = 1 << 0;
   compact = 1 << 1;