test: complete coverage for lib/assert.js

6481c93 modified `lib/assert.js` and added some tests for new
functionality, but left a single line uncovered by tests. This adds a
test that covers the currently-uncovered line (which is the final
`return` statement in `setHasSimilarElement()`).`

PR-URL: #12239
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/parallel/test-assert-deep.js

@@ -107,6 +107,11 @@ for (const a of similar) {
   }
 }
 
+assert.throws(
+  () => { assert.deepEqual(new Set([{a: 0}]), new Set([{a: 1}])); },
+  /^AssertionError: Set { { a: 0 } } deepEqual Set { { a: 1 } }$/
+);
+
 function assertDeepAndStrictEqual(a, b) {
   assert.deepEqual(a, b);
   assert.deepStrictEqual(a, b);