Drive-by fix for unnecessary `&mut`
Drive-by fix for unnecessary `&mut`

aidancully/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust