cmd/link/internal/loadpe: update comment about @feat.00 symbol handling

cmd/link/internal/loadpe: update comment about @feat.00 symbol handling

The @feat.00 comment is outdated, as Go does support SEH on
windows/amd64. While here, simplify it and add a link to the
relevant documentation.

Change-Id: I6e3c786ca4f4809baf46015edf569d06b12f1239
Reviewed-on: https://go-review.googlesource.com/c/go/+/550635
Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Quim Muntal <quimmuntal@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>