Rust version policy: Debian 13 (Trixie) was released

Debian 13 (Trixie) was released with Rust 1.85.0, which is enough for
building the kernel.

Thus document it.

This matches the pending documentation update in the kernel side [1].

Link: https://lore.kernel.org/rust-for-linux/20251101094011.1024534-1-ojeda@kernel.org/ [1]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: ojeda

src/Rust-version-policy.md

@@ -19,7 +19,7 @@ In addition, one of the three [flagship goals for 2024H2](https://rust-lang.gith
 The Rust versions currently supported should already be enough for kernel developers in distributions that provide recent Rust compilers routinely, such as:
 
   - Arch Linux.
-  - Debian Testing and Unstable (outside the freeze period).
+  - Debian 13 (Trixie), Debian Testing and Debian Unstable (Sid).
   - Fedora Linux.
   - Gentoo Linux.
   - Nix (unstable).