test: add mustCall to test-fs-readfile-pipe-large

PR-URL: https://github.com/nodejs/node/pull/27460


Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Yorkie Liu <yorkiefixer@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ouyang Yadong <oyydoibh@gmail.com>