remove pointless cold_path impl in interpreter

src/intrinsics/mod.rs

@@ -1264,6 +1264,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
 
         sym::cold_path => {
             // This is a no-op. The intrinsic is just a hint to the optimizer.
+            // We still have an impl here to avoid it being turned into a call.
         }
 
         // Unimplemented intrinsics must have a fallback body. The fallback body is obtained