Fix some warnings from outdated code

Author: thomcc

src/codegen/swap_bytes.rs

@@ -15,7 +15,7 @@ macro_rules! impl_swap_bytes {
             impl SwapBytes for $id {
                 #[inline]
                 fn swap_bytes(self) -> Self {
-                    unsafe { shuffle!(self, [1, 0]) }
+                    shuffle!(self, [1, 0])
                 }
             }
         )+

src/lib.rs

@@ -217,7 +217,6 @@
     rustc_attrs,
     platform_intrinsics,
     stdsimd,
-    aarch64_target_feature,
     arm_target_feature,
     link_llvm_intrinsics,
     core_intrinsics,