Tweak non-char/numeric in range pattern diagnostic

[estebank]

We currently emit:

error[E0029]: only char and numeric types are allowed in range patterns
 --> src/main.rs:4:12
  |
4 |         0.."" => {}
  |            ^^ ranges require char or numeric types
  |
  = note: start type: {integer}
  = note: end type: &'static str

But it should be closer to:

error[E0029]: only char and numeric types are allowed in range patterns
 --> src/main.rs:4:12
  |
4 |         0.."" => {}
  |         -  ^^ this is of type `&'static str` but it should be `char` or numeric
  |         |
  |         this is of type `{integer}`