Add a comment about dead code

src/memmem/prefilter/mod.rs

@@ -316,8 +316,11 @@ pub(crate) fn forward(
     }
     #[cfg(all(not(miri), target_arch = "wasm32", memchr_runtime_simd))]
     {
+        // SAFETY: `wasm::find` is actually a safe function
+        //
+        // Also note that the `if true` is here to prevent, on wasm with simd,
+        // rustc warning about the code below being dead code.
         if true {
-            // SAFETY: `wasm::find` is actually a safe function
             return unsafe { Some(PrefilterFn::new(wasm::find)) };
         }
     }