Revert "Making D3D12 accept InternalUsageDescriptors"

This reverts commit 365d40b93a.

Reason for revert: Broke the ChromeOS build in the Dawn roll.
https://chromium-review.googlesource.com/c/chromium/src/+/3090302

Original change's description:
> Making D3D12 accept InternalUsageDescriptors
>
> This is a follow up from two previous CLs,
> https://dawn-review.googlesource.com/c/dawn/+/58440
> and
> https://dawn-review.googlesource.com/c/dawn/+/58140
>
> This CL adds in the D3D12Backend the possibility to use Dawn Texture
> Internal Usage Descriptor, and adds a series of tests to validate it.
>
> Change-Id: I94f6b39153b60ec8af61bda22d41a865898da613
> Bug: dawn:1027, dawn:1052
> Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/61520
> Commit-Queue: Juanmi Huertas <juanmihd@chromium.org>
> Reviewed-by: Kai Ninomiya <kainino@chromium.org>

TBR=kainino@chromium.org,enga@chromium.org,juanmihd@chromium.org,dawn-scoped@luci-project-accounts.iam.gserviceaccount.com

Change-Id: I11b246f38505df23a6c61e851d6d90e34c8d1287
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: dawn:1027, dawn:1052
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/61820
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Austin Eng <enga@chromium.org>

src/include/dawn_native/D3D12Backend.h

@@ -79,7 +79,6 @@ namespace dawn_native { namespace d3d12 {
         // Contents of WGPUTextureDescriptor are stored individually since the descriptor
         // could outlive this image.
         WGPUTextureUsageFlags mUsage;
-        WGPUTextureUsageFlags mUsageInternal = WGPUTextureUsage_None;
         WGPUTextureDimension mDimension;
         WGPUExtent3D mSize;
         WGPUTextureFormat mFormat;