const &str now requires explicit lifetime

[rsofaer]

Minimal example: Permalink to the playground

use vstd::prelude::*;

verus! {
  const C: &str = "str";
}

Gives error message:

error[[E0106]](https://doc.rust-lang.org/stable/error_codes/E0106.html): missing lifetime specifier
 --> /playground/src/main.rs:4:10
  |
4 | const C: &str = "str";
  |          ^ expected named lifetime parameter
  |
  = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
help: consider using the `'static` lifetime, but this is uncommon unless you're returning a borrowed value from a `const` or a `static`
  |
4 | const C: &'static str = "str";
  |           +++++++
help: instead, you are more likely to want to return an owned value
  |
4 - const C: &str = "str";
4 + const C: String = "str";
  |

error: aborting due to 1 previous error

This is irritating because when annotated with 'static, the code gives a warning in rustc for an unneeded lifetime specifier.