Remove allow(unused_mut) due to the rustc bug (#319)

Author: JohnTitor

src/api/ops/scalar_shifts.rs

@@ -36,11 +36,8 @@ macro_rules! impl_ops_scalar_shifts {
                     use super::*;
                     #[cfg_attr(not(target_arch = "wasm32"), test)] #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
                     #[cfg_attr(any(target_arch = "s390x", target_arch = "sparc64"),
-                               allow(unreachable_code,
-                                     unused_variables,
-                                     unused_mut)
+                               allow(unreachable_code, unused_variables)
                     )]
-                    // ^^^ FIXME: https://github.com/rust-lang/rust/issues/55344
                     #[cfg(not(target_arch = "aarch64"))]
                     //~^ FIXME: https://github.com/rust-lang/packed_simd/issues/317
                     fn ops_scalar_shifts() {

src/api/ops/vector_shifts.rs

@@ -37,11 +37,8 @@ macro_rules! impl_ops_vector_shifts {
                     use super::*;
                     #[cfg_attr(not(target_arch = "wasm32"), test)] #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
                     #[cfg_attr(any(target_arch = "s390x", target_arch = "sparc64"),
-                               allow(unreachable_code,
-                                     unused_variables,
-                                     unused_mut)
+                               allow(unreachable_code, unused_variables)
                     )]
-                    // ^^^ FIXME: https://github.com/rust-lang/rust/issues/55344
                     #[cfg(not(target_arch = "aarch64"))]
                     //~^ FIXME: https://github.com/rust-lang/packed_simd/issues/317
                     fn ops_vector_shifts() {

src/api/reductions/float_arithmetic.rs

@@ -144,8 +144,6 @@ macro_rules! impl_reduction_float_arithmetic {
                     #[cfg_attr(not(target_arch = "wasm32"), test)]
                     #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
                     #[allow(unreachable_code)]
-                    #[allow(unused_mut)]
-                    // ^^^ FIXME: https://github.com/rust-lang/rust/issues/55344
                     fn sum_nan() {
                         // FIXME: https://bugs.llvm.org/show_bug.cgi?id=36732
                         // https://github.com/rust-lang-nursery/packed_simd/issues/6
@@ -175,8 +173,6 @@ macro_rules! impl_reduction_float_arithmetic {
                     #[cfg_attr(not(target_arch = "wasm32"), test)]
                     #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
                     #[allow(unreachable_code)]
-                    #[allow(unused_mut)]
-                    // ^^^ FIXME: https://github.com/rust-lang/rust/issues/55344
                     fn product_nan() {
                         // FIXME: https://bugs.llvm.org/show_bug.cgi?id=36732
                         // https://github.com/rust-lang-nursery/packed_simd/issues/6