Remove the file session.rs in crate/zed which is no longer used (#15394)

There was an empty file *session.rs* in the crate zed which was empty so
I am going ahead and removing it...

Release Notes:

- N/A

crates/zed/src/zed.rs

@@ -5,7 +5,6 @@ pub(crate) mod linux_prompts;
 #[cfg(not(target_os = "linux"))]
 pub(crate) mod only_instance;
 mod open_listener;
-pub(crate) mod session;
 
 pub use app_menus::*;
 use breadcrumbs::Breadcrumbs;

crates/zed/src/zed/session.rs

@@ -1 +0,0 @@
-