Previously we use the error message for normal invalid private member
access, so for a failed brand check for class C, the error is

TypeError: Cannot read private member C from an object whose class did not declare it

This updates the message to

TypeError: Object must be an instance of class C

Bug: v8:8330
Change-Id: Ida98f46b8387631194a9b7a48bd1f419045ac6e7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2100688
Commit-Queue: Joyee Cheung <joyee@igalia.com>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66923}