Fix implicit lifetime for Rust 1.78

[sbihel]

No description provided.

[timothee-haudebourg]

For the record, what was the error exactly?

[sbihel]

For the record, what was the error exactly?

error[E0309]: the parameter type `R` may not live long enough
   --> /Users/sbihel/.cargo/git/checkouts/treeldr-779b41ff6593b58b/9313354/layouts/src/matching.rs:110:32
    |
98  | impl<'a, 'p, R, D, Q> Iterator for Matching<'a, 'p, R, D, Q>
    |      -- the parameter type `R` must be valid for the lifetime `'a` as defined here...
...
110 |                     Some(quad_state) => match quad_state.quad_matching.next() {
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `R` will meet its required lifetime bounds
    |
help: consider adding an explicit lifetime bound
    |
100 |     R: Clone + PartialEq + 'a,
    |                          ++++