Revert "Vulkan: Fallback to XCB for Xlib surfaces"

This reverts commit fb0bf70459.

Reason for revert: Failing build during roll:
https://chromium-review.googlesource.com/c/chromium/src/+/2686267/2

Original change's description:
> Vulkan: Fallback to XCB for Xlib surfaces
>
> Chromium builds the Vulkan loader without support Xlib (because it
> prefers XCB) which caused Xlib wgpu::SwapChain creation to fail on the
> Vulkan backend.
>
> This CL adds a fallback to use VK_KHR_xcb_surface if VK_KHR_xlib_surface
> isn't present.
>
> Bug: dawn:662
> Change-Id: I0e0128ee6b5c75da03998dbae231d17e48bacc81
> Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/41180
> Reviewed-by: Austin Eng <enga@chromium.org>
> Commit-Queue: Austin Eng <enga@chromium.org>
> Auto-Submit: Corentin Wallez <cwallez@chromium.org>

TBR=cwallez@chromium.org,jiawei.shao@intel.com,hao.x.li@intel.com,enga@chromium.org

Change-Id: Ia8d2ffb715260b1de490ca04cc76f41bb60b1f61
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: dawn:662
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/41343
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Kai Ninomiya <kainino@chromium.org>

src/common/vulkan_platform.h

@@ -162,7 +162,6 @@ namespace dawn_native { namespace vulkan {
 
 #if defined(DAWN_USE_X11)
 #    define VK_USE_PLATFORM_XLIB_KHR
-#    define VK_USE_PLATFORM_XCB_KHR
 #    include "common/xlib_with_undefs.h"
 #endif  // defined(DAWN_USE_X11)
 

src/common/xlib_with_undefs.h

@@ -24,7 +24,6 @@
 // This header includes <X11/Xlib.h> but removes all the extra defines that conflict with
 // identifiers in internal code. It should never be included in something that is part of the public
 // interface.
-#include <X11/Xlib-xcb.h>
 #include <X11/Xlib.h>
 
 #undef Success