test: prepare test-assert for strictEqual linting

Make minor modifications to test-assert.js to prepare it for linting
rule that forbids the use of string literals for the third argument of
assert.strictEqual().

Backport-PR-URL: #22888
PR-URL: #22849
Reviewed-By: Teddy Katz <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Trivikram Kamat <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>

Author: Trott

test/parallel/test-assert.js

@@ -610,11 +610,11 @@ try {
 }
 
 try {
-  assert.strictEqual(1, 2, 'oh no');
+  assert.strictEqual(1, 2, 'oh no'); // eslint-disable-line no-restricted-syntax
 } catch (e) {
   assert.strictEqual(e.message.split('\n')[0], 'oh no');
-  assert.strictEqual(e.generatedMessage, false,
-                     'Message incorrectly marked as generated');
+  // Message should not be marked as generated.
+  assert.strictEqual(e.generatedMessage, false);
 }
 
 {