internal/memory: skip TestRead on darwin
internal/memory: skip TestRead on darwin

Test fails because macOS doesn't have a /proc/meminfo.

Change-Id: I247331a0a8cbdd07ba0928ad5845db3190d39bbe
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/425201
Reviewed-by: Julie Qiu <e6cb64861edcc38971590ff27c111e0e672de045@google.com>
Run-TryBot: Damien Neil <7e091e9a80da888fcd7836fd3c6b7b85f4677c12@google.com>
TryBot-Result: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite