Remove unused SamplingRoutineCache::Key::operator<

Bug: b/141863676
Change-Id: Ie6ea68edcc0505bf2931c0fe91e4be418c4a21e0
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/37108
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Antonio Maiorano <amaiorano@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
diff --git a/src/Vulkan/VkDevice.hpp b/src/Vulkan/VkDevice.hpp
index b27fa50..3fa0afe 100644
--- a/src/Vulkan/VkDevice.hpp
+++ b/src/Vulkan/VkDevice.hpp
@@ -72,7 +72,6 @@
 			uint32_t imageView;
 
 			inline bool operator == (const Key& rhs) const;
-			inline bool operator < (const Key& rhs) const;
 
 			struct Hash
 			{
@@ -121,11 +120,6 @@
 	return instruction == rhs.instruction && sampler == rhs.sampler && imageView == rhs.imageView;
 }
 
-inline bool vk::Device::SamplingRoutineCache::Key::operator < (const Key& rhs) const
-{
-	return std::tie(instruction, sampler, imageView) < std::tie(rhs.instruction, rhs.sampler, rhs.imageView);
-}
-
 inline std::size_t vk::Device::SamplingRoutineCache::Key::Hash::operator() (const Key& key) const noexcept
 {
 	// Combine three 32-bit integers into a 64-bit hash.