test: fix wrong method call

PR-URL: #34629
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ricky Zhou <0x19951125@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-fs-write-reuse-callback.js

@@ -35,5 +35,5 @@ const ondone = common.mustCall((err) => {
 write();
 function write() {
   const buf = Buffer.alloc(size, 'x');
-  fs.write(fd, buf, 0, buf.size, -1, ondone);
+  fs.write(fd, buf, 0, buf.length, -1, ondone);
 }