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/terminal_view/src/terminal_panel.rs

@@ -31,7 +31,7 @@ use workspace::{
 
 use anyhow::Result;
 
-const TERMINAL_PANEL_KEY: &'static str = "TerminalPanel";
+const TERMINAL_PANEL_KEY: &str = "TerminalPanel";
 
 actions!(terminal_panel, [ToggleFocus]);