Update simd.rs

Fixed typo

Author: vayunbiyani

library/core/src/intrinsics/simd.rs

@@ -13,7 +13,7 @@ extern "rust-intrinsic" {
     #[rustc_nounwind]
     pub fn simd_insert<T, U>(x: T, idx: u32, val: U) -> T;
 
-    /// Extracts an element frozm a vector.
+    /// Extracts an element from a vector.
     ///
     /// `T` must be a vector with element type `U`.
     ///