runtime/pprof: fix TestCPUProfileWithFork on Windows/ARM
runtime/pprof: fix TestCPUProfileWithFork on Windows/ARM

Use smaller heap on Windows/ARM, which generally does not have
page file enabled and therefore has limited virtual address space.

Updates #26148

Signed-off-by: Jordan Rhee <jordanrh@microsoft.com>

Change-Id: I4030be24a10fab7b9b659e3736b7e83f10710bfa
Reviewed-on: https://go-review.googlesource.com/c/153719
Run-TryBot: Hyang-Ah Hana Kim <d7e82c3c07f92613bcbf9a1e88f6b96c13caa3b0@gmail.com>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

cloudflare/go,cloudflare/go,josharian/go,akutz/go,josharian/go,cloudflare/go,golang/go,akutz/go,CAFxX/go,CAFxX/go,cloudflare/go,nawawi/go,cloudflare/go,cloudflare/go,akutz/go,josharian/go,nawawi/go,nawawi/go,nawawi/go,CAFxX/go,CAFxX/go,akutz/go,CAFxX/go,golang/go,nawawi/go,golang/go,akutz/go,josharian/go,CAFxX/go,golang/go,cloudflare/go,nawawi/go,cloudflare/go,nawawi/go,CAFxX/go,nawawi/go,akutz/go,akutz/go,golang/go,golang/go,josharian/go,josharian/go,josharian/go,golang/go,golang/go,CAFxX/go,josharian/go,akutz/go