test: improve assertion in test-inspector.js

Remove an unecessary string literal from assert.strictEqual() call in
test-inspector.js. The string literal is printed instead of the value
that causes an error. Removing the string literal allows the value that
caused the error to be printed. This improves the troubleshooting
experience when the test fails due to that assertion.

Backport-PR-URL: #22888
PR-URL: #22849
Reviewed-By: Teddy Katz <teddy.katz@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Author: Trott

test/sequential/test-inspector.js

@@ -33,8 +33,7 @@ function checkBadPath(err) {
 }
 
 function checkException(message) {
-  assert.strictEqual(message.exceptionDetails, undefined,
-                     'An exception occurred during execution');
+  assert.strictEqual(message.exceptionDetails, undefined);
 }
 
 function assertNoUrlsWhileConnected(response) {