Incorrect span in `&mut` suggestion

[estebank]

#48914 introduces a suggestion with an incorrect span:

error[E0594]: cannot assign to data in a `&` reference
  --> $DIR/issue-47388.rs:18:5
   |
LL |     let fancy_ref = &(&mut fancy);
   |                     ------------- help: consider changing this to be a mutable reference: `&mut`
LL |     fancy_ref.num = 6; //~ ERROR E0594
   |     ^^^^^^^^^^^^^^^^^ `fancy_ref` is a `&` reference, so the data it refers to cannot be written

The output should be either

LL |     let fancy_ref = &(&mut fancy);
   |                     - help: consider changing this to be a mutable reference: `&mut `

or

LL |     let fancy_ref = &(&mut fancy);
   |                     ------------- help: consider changing this to be a mutable reference: `&mut (&mut fancy)`