test: fix assert.strictEqual argument order

The arguments to assert.strictEqual in a number of calls were in the
wrong order. It is preferred that literal values are in the second
argument.

Updates test/parallel/test-fs-readStream.js

PR-URL: https://github.com/nodejs/node/pull/24172


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>