test: fix test/pummel/test-fs-largefile.js

test-fs-largefile.js calls `fs.close()` without a callback which results
in an error as of Node.js 10.0.0. Add a `common.mustCall()` callback so
the test passes again.

PR-URL: https://github.com/nodejs/node/pull/25372


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>