Fix two nightly errors - Githubissues

Currently, we have these two errors on rust nightly. It would be nice to help rustc understand what's going on

error[E0658]: anonymous lifetimes in `impl Trait` are unstable
   --> filter-parser/src/lib.rs:173:53
    |
173 | fn ws<'a, O>(inner: impl FnMut(Span<'a>) -> IResult<O>) -> impl FnMut(Span<'a>) -> IResult<O> {
    |                                                     ^ expected named lifetime parameter
    |
    = help: add `#![feature(anonymous_lifetime_in_impl_trait)]` to the crate attributes to enable
help: consider introducing a named lifetime parameter
    |
173 | fn ws<'a, 'a, O>(inner: impl FnMut(Span<'a>) -> IResult<'a, O>) -> impl FnMut(Span<'a>) -> IResult<O> {
    |       +++                                               +++

error[E0658]: anonymous lifetimes in `impl Trait` are unstable
  --> filter-parser/src/error.rs:36:49
   |
36 |     mut parser: impl FnMut(Span<'a>) -> IResult<O>,
   |                                                 ^ expected named lifetime parameter
   |
   = help: add `#![feature(anonymous_lifetime_in_impl_trait)]` to the crate attributes to enable
help: consider introducing a named lifetime parameter
   |
35 ~ pub fn cut_with_err<'a, 'a, O>(
36 ~     mut parser: impl FnMut(Span<'a>) -> IResult<'a, O>,
   |

For more information about this error, try `rustc --explain E0658`.
error: could not compile `filter-parser` due to 2 previous errors

meilisearch / milli

Fix two nightly errors #740