Fix wording in shift functions doc comments
diff --git a/src/tools/miri/src/shims/x86/mod.rs b/src/tools/miri/src/shims/x86/mod.rs
index cf3c375..cd4e1c2 100644
--- a/src/tools/miri/src/shims/x86/mod.rs
+++ b/src/tools/miri/src/shims/x86/mod.rs
@@ -488,7 +488,7 @@ enum ShiftOp {
///
/// For logic shifts, when right is larger than BITS - 1, zero is produced.
/// For arithmetic right-shifts, when right is larger than BITS - 1, the sign
-/// bit is copied to remaining bits.
+/// bit is copied to all bits.
fn shift_simd_by_scalar<'tcx>(
this: &mut crate::MiriInterpCx<'_, 'tcx>,
left: &OpTy<'tcx, Provenance>,
@@ -544,7 +544,7 @@ fn shift_simd_by_scalar<'tcx>(
///
/// For logic shifts, when right is larger than BITS - 1, zero is produced.
/// For arithmetic right-shifts, when right is larger than BITS - 1, the sign
-/// bit is copied to remaining bits.
+/// bit is copied to all bits.
fn shift_simd_by_simd<'tcx>(
this: &mut crate::MiriInterpCx<'_, 'tcx>,
left: &OpTy<'tcx, Provenance>,
