Revert "Add ComparisonSampler binding type and validation tests"

This reverts commit 6d9e4f8076.

Reason for revert: Breaks the roll in Chromium, gpu_sampler.cc must first be
fixed to use the new undefined value, before this can be landed.

Original change's description:
> Add ComparisonSampler binding type and validation tests
> 
> Bug: dawn:367
> Change-Id: Iba1d3d03f6247a356b6f3fabfe7a7ba3c0753171
> Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/18423
> Reviewed-by: Austin Eng <enga@chromium.org>
> Commit-Queue: Austin Eng <enga@chromium.org>

TBR=cwallez@chromium.org,kainino@chromium.org,enga@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: dawn:367
Change-Id: Ic071a601df2063bd2da5388b2e75c1a121924a69
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/19983
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

src/dawn_native/Sampler.cpp

@@ -80,10 +80,6 @@ namespace dawn_native {
         return new SamplerBase(device, ObjectBase::kError);
     }
 
-    bool SamplerBase::HasCompareFunction() const {
-        return mCompareFunction != wgpu::CompareFunction::Undefined;
-    }
-
     size_t SamplerBase::HashFunc::operator()(const SamplerBase* module) const {
         size_t hash = 0;