Remove GMB type checks from MediaFoundationVideoEncodeAccelerator.

Remove some unnecessary GMB type checks from
MediaFoundationVideoEncodeAccelerator. A valid GpuMemoryBuffer can only
have GMB type as DXGI_SHARED_HANDLE or SHARED_MEMORY_BUFFER and is never
EMPTY_BUFFER.

Bug: 40263579
Change-Id: Ie112498718093c3a4aed01e69622d9e73f294856
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5496385
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Auto-Submit: vikas soni <vikassoni@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1294427}