assert: avoid potentially misleading reference to object identity

Often, the word “identical” when referring to JS objects will
be read as referring to having the same object identity (which is
called “reference equality” here), but what the error message is
trying to say here is that the objects are different but yield the
same `util.inspect()` output.

Since `util.inspect()` output represents the structure rather than
the identity of objects, (hopefully) clarify the error message to
reflect that.

PR-URL: https://github.com/nodejs/node/pull/28824


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>