benchmark,child_process: remove failing benchmark parameter

A 16 MiB strings seems to be too large to be send to the parent process,
making the whole benchmark throws.

PR-URL: #36295
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

benchmark/child_process/child-process-read-ipc.js

@@ -13,7 +13,7 @@ if (process.argv[2] === 'child') {
   const bench = common.createBenchmark(main, {
     len: [
       64, 256, 1024, 4096, 16384, 65536,
-      65536 << 4, 65536 << 8,
+      65536 << 4, 65536 << 6 - 1,
     ],
     dur: [5]
   });