Disable rust_2024_compatibility lint option (#9615)

Compiling with nightly rust compiler, I'm getting a lot of errors like
this:

    error: `if let` assigns a shorter lifetime since Edition 2024
       --> proxy/src/auth/backend/jwt.rs:226:16
        |
    226 |             if let Some(permit) = self.try_acquire_permit() {
        |                ^^^^^^^^^^^^^^^^^^^-------------------------
        |                                   |
| this value has a significant drop implementation which may observe a
major change in drop order and requires your discretion
        |
        = warning: this changes meaning in Rust 2024
= note: for more information, see issue #124085
<rust-lang/rust#124085>
    help: the value is now dropped here in Edition 2024
       --> proxy/src/auth/backend/jwt.rs:241:13
        |
    241 |             } else {
        |             ^
    note: the lint level is defined here
       --> proxy/src/lib.rs:8:5
        |
    8   |     rust_2024_compatibility
        |     ^^^^^^^^^^^^^^^^^^^^^^^
= note: `#[deny(if_let_rescope)]` implied by
`#[deny(rust_2024_compatibility)]`

and this:

error: these values and local bindings have significant drop
implementation that will have a different drop order from that of
Edition 2021
       --> proxy/src/auth/backend/jwt.rs:376:18
        |
    369 |         let client = Client::builder()
| ------ these values have significant drop implementation and will
observe changes in drop order under Edition 2024
    ...
    376 |             map: DashMap::default(),
        |                  ^^^^^^^^^^^^^^^^^^
        |
        = warning: this changes meaning in Rust 2024
= note: for more information, see issue #123739
<rust-lang/rust#123739>
= note: `#[deny(tail_expr_drop_order)]` implied by
`#[deny(rust_2024_compatibility)]`

They are caused by the `rust_2024_compatibility` lint option.

When we actually switch to the 2024 edition, it makes sense to go
through all these and check that the drop order changes don't break
anything, but in the meanwhile, there's no easy way to avoid these
errors. Disable it, to allow compiling with nightly again.

Co-authored-by: Arpad Müller <arpad-m@users.noreply.github.com>

proxy/src/lib.rs

@@ -1,12 +1,6 @@
 // rustc lints/lint groups
 // https://doc.rust-lang.org/rustc/lints/groups.html
-#![deny(
-    deprecated,
-    future_incompatible,
-    let_underscore,
-    nonstandard_style,
-    rust_2024_compatibility
-)]
+#![deny(deprecated, future_incompatible, let_underscore, nonstandard_style)]
 #![warn(clippy::all, clippy::pedantic, clippy::cargo)]
 // List of denied lints from the clippy::restriction group.
 // https://rust-lang.github.io/rust-clippy/master/index.html#?groups=restriction