gopls/internal/lsp/cache: suppress crashes in fact_purity analyzer
gopls/internal/lsp/cache: suppress crashes in fact_purity analyzer

It has a known bug, and the purpose of the PanicOnBugs is to
find unknown bugs.

Updates golang/go#54762
Updates golang/go#56035

Change-Id: Id9fdfff478ef52b1d864acee366991808baeb574
Reviewed-on: https://go-review.googlesource.com/c/tools/+/440178
Run-TryBot: Alan Donovan <7069e9552f9d110b0a0f326b96f22f63fb99dfc1@google.com>
Reviewed-by: Robert Findley <9179eee875d1ee628c37fb47d7e749e855ffd21f@google.com>
gopls-CI: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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