net/http/pprof: skip TestDeltaProfile on all arm and arm64 architectures

Given that we have seen failures with the same failure mode on both
openbsd/arm and android/arm64, it seems likely that the underlying bug
affects at least all ARM-based architectures.

It appears that either these architectures are not able to sample at
the frequency expected by the test, or the samples are for some reason
being dropped.

For #50218

Change-Id: I42a6c8ecda57448f8068e8facb42a4a2cecbbb37
Reviewed-on: https://go-review.googlesource.com/c/go/+/383997


Trust: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>