mesa: fix build with gcc15

- remove `rustPlatform.bindgenHook` from `buildInputs`,
`rustPlatform.bindgenHook` adds gcc headers to `BINDGEN_EXTRA_CLANG_ARGS`
which somehow conflict more with gcc15 than gcc14.
Removing hook should let meson use bindgen from cli with clang libraries.

Fixes bindgen error building `mesa` with gcc15:
```
FAILED: [code=1] src/nouveau/compiler/nak_bindings.rs
/nix/store/rm899xgm82kanr814dk8siwyghyxwphg-rust-bindgen-0.72.0/bin/bindgen
../src/nouveau/compiler/nak_bindings.h ...
/build/source/src/nouveau/winsys/./nouveau_bo.h:41:4: error: unknown
type name 'atomic_uint_fast32_t'
Unable to generate bindings: clang diagnosed error:
/build/source/src/nouveau/winsys/./nouveau_bo.h:41:4: error: unknown
type name 'atomic_uint_fast32_t'
```

pkgs/development/libraries/mesa/default.nix

@@ -29,7 +29,6 @@
   runCommand,
   rust-bindgen,
   rust-cbindgen,
-  rustPlatform,
   rustc,
   spirv-llvm-translator,
   stdenv,
@@ -314,7 +313,6 @@ stdenv.mkDerivation {
     rustc
     rust-bindgen
     rust-cbindgen
-    rustPlatform.bindgenHook
     wayland-scanner
   ]
   ++ lib.optionals needNativeCLC [