Remove unreachable code when setting barrier features on Apple Silicon.

MVKPhysicalDeviceMetalFeatures::memoryBarriers and ::textureBarriers
are never enabled on Apple Silicon. Remove it as an possibility.
diff --git a/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm b/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm
index 7ef37f5..ebe0114 100644
--- a/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm
+++ b/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm
@@ -1465,10 +1465,6 @@
 			if (supportsMTLGPUFamily(Apple7)) {
 				_metalFeatures.maxQueryBufferSize = (256 * KIBI);
 			}
-		} else {
-			// Apple devices don't like barriers in render passes.
-			_metalFeatures.memoryBarriers = true;
-			_metalFeatures.textureBarriers = true;
 		}
 	} else
 #endif