Update library/alloc/src/collections/vec_deque.rs
Update library/alloc/src/collections/vec_deque.rs

Replace lshift with multiply

Co-authored-by: Mara Bos <4b4419d6612c6ced3b00e27e77e81acad5ca175b@m-ou.se>
graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust