test: allow slightly more diff in memory leak test

Previous limit was too low for debug builds.

PR-URL: #51362
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>

test/parallel/test-crypto-dh-leak.js

@@ -26,4 +26,4 @@ const after = process.memoryUsage.rss();
 
 // RSS should stay the same, ceteris paribus, but allow for
 // some slop because V8 mallocs memory during execution.
-assert(after - before < 10 << 20, `before=${before} after=${after}`);
+assert(after - before < 10 << 21, `before=${before} after=${after}`);