Also remove MemorySnapshotWin since the code is identical to
MemorySnapshotGeneric now.
Bug: crashpad:95
Change-Id: I9a631f8eb206dd72a69158021db87e8db41c5913
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/1642148
Reviewed-by: Mark Mentovai <mark@chromium.org>
Reviewed-by: Vlad Tsyrklevich <vtsyrklevich@chromium.org>
Commit-Queue: Clark DuVall <cduvall@chromium.org>