test: fix test-worker-memory.js for large cpu #s

This test consistently failed on a system with a
large number of cores (~120). Cap the number of
concurrent workers so we'll stay consistently within
the "slack" allowed with respect to rss.

PR-URL: #27090
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>

Author: mhdawson

Diff for: test/parallel/test-worker-memory.js

@@ -4,7 +4,13 @@ const assert = require('assert');
 const util = require('util');
 const { Worker } = require('worker_threads');
 
-const numWorkers = +process.env.JOBS || require('os').cpus().length;
+let numWorkers = +process.env.JOBS || require('os').cpus().length;
+if (numWorkers > 20) {
+  // Cap the number of workers at 20 (as an even divisor of 60 used as
+  // the total number of workers started) otherwise the test fails on
+  // machines with high core counts.
+  numWorkers = 20;
+}
 
 // Verify that a Worker's memory isn't kept in memory after the thread finishes.