test: use global.gc() instead of gc()

This change is made for consistency, and to remove an
eslint-disable comment.

PR-URL: https://github.com/nodejs/node/pull/25012
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/parallel/test-fs-filehandle.js

@@ -31,6 +31,6 @@ common.expectWarning({
   ]
 });
 
-gc();  // eslint-disable-line no-undef
+global.gc();
 
 setTimeout(() => {}, 10);