Remove test cases for field overflows in intarray and ltree.

Remove test cases for field overflows in intarray and ltree.

These checks are failing in the buildfarm, reporting stack overflows
rather than the expected errors, though seemingly only on ppc64 and
s390x platforms.  Perhaps there is something off about our tests
for stack depth on those architectures?  But there's no time to
debug that right now, and surely these tests aren't too essential.
Revert for now and plan to revisit after the release dust settles.

Backpatch-through: 14
Security: CVE-2026-6473