runtime: skip TestCrashDumpsAllThreads on openbsd/arm
runtime: skip TestCrashDumpsAllThreads on openbsd/arm

This test is also now flakey on this platform.

Updates #36435
Updates #42464

Change-Id: Idedb81478178ffffe7a9c125a6e8bbd83458f9ab
Reviewed-on: https://go-review.googlesource.com/c/go/+/315794
Trust: Joel Sing <4816dabf8db1bc6cac35b3a24cab2ff844b5b0c7@sing.id.au>
Reviewed-by: Cherry Mui <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>

nawawi/go,nawawi/go,nawawi/go,golang/go,CAFxX/go,nawawi/go,golang/go,golang/go,CAFxX/go,golang/go,cloudflare/go,cloudflare/go,cloudflare/go,cloudflare/go,golang/go,cloudflare/go,golang/go,golang/go,cloudflare/go,nawawi/go,nawawi/go,CAFxX/go,cloudflare/go,CAFxX/go,CAFxX/go,CAFxX/go,nawawi/go,cloudflare/go,CAFxX/go,CAFxX/go,nawawi/go,golang/go