Remove unneeded 'static lifetimes on &strs in constants (#8698)

This PR removes unneeded `'static` lifetimes on `&str`s stored in
`const` declarations.

This addresses some Clippy lints about
[`redundant_static_lifetimes`](https://rust-lang.github.io/rust-clippy/master/index.html#/redundant_static_lifetimes).

In item-level `const` declarations we can rely on lifetime elision and
use the default `'static` lifetime.

Note that associated constants still require an explicit `'static`
lifetime, as explained in
https://github.com/rust-lang/rust/issues/115010.

Release Notes:

- N/A

crates/gpui/src/platform/mac/metal_renderer.rs

@@ -26,8 +26,7 @@ pub(crate) type PointF = crate::Point<f32>;
 #[cfg(not(feature = "runtime_shaders"))]
 const SHADERS_METALLIB: &[u8] = include_bytes!(concat!(env!("OUT_DIR"), "/shaders.metallib"));
 #[cfg(feature = "runtime_shaders")]
-const SHADERS_SOURCE_FILE: &'static str =
-    include_str!(concat!(env!("OUT_DIR"), "/stitched_shaders.metal"));
+const SHADERS_SOURCE_FILE: &str = include_str!(concat!(env!("OUT_DIR"), "/stitched_shaders.metal"));
 const INSTANCE_BUFFER_SIZE: usize = 2 * 1024 * 1024; // This is an arbitrary decision. There's probably a more optimal value (maybe even we could adjust dynamically...)
 
 pub type Context = Arc<Mutex<Vec<metal::Buffer>>>;