test: replace assert.equal with assert.strictEqual

PR-URL: https://github.com/nodejs/node/pull/18119


Reviewed-By: Shingo Inoue <leko.noor@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>