go/types/objectpath: update objectpath tests for TypeString changes
go/types/objectpath: update objectpath tests for TypeString changes

Enable a test case that uses comparable, now that its type string
has been adjusted.

Follow-up for CL 380999.

Change-Id: I5ce729e42234d7539a464d0aafba5a7f53d59625
Reviewed-on: https://go-review.googlesource.com/c/tools/+/381234
Trust: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>
Run-TryBot: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>
gopls-CI: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Robert Findley <9179eee875d1ee628c37fb47d7e749e855ffd21f@google.com>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools