No longer autoload deprecated-dirs (nushell#14242)

# Description

Follow-up to nushell#13842. In that commit, using one of the `dirs`/`shells`
aliases would notify the user that it would no longer be autoloaded in
future releases. This is the removal stage.

Side-benefit: Additional 1ms+ load time improvement

# User-Facing Changes

Breaking-change - `dirs` aliases are no longer autoloaded.

Users can either choose to continue using the aliases by adding the
following to the startup:

```nu
use std/dirs shells-aliases *
```

Alternatively, users can use the `dirs` subcommands (rather than the
aliases) with:

```nu
use std/dirs
```

Author: NotTheDr01ds

crates/nu-std/src/lib.rs

@@ -54,12 +54,6 @@ pub fn load_standard_library(
         ("mod.nu", "std/math", include_str!("../std/math/mod.nu")),
         ("mod.nu", "std/util", include_str!("../std/util/mod.nu")),
         ("mod.nu", "std/xml", include_str!("../std/xml/mod.nu")),
-        // Remove in following release
-        (
-            "mod.nu",
-            "std/deprecated_dirs",
-            include_str!("../std/deprecated_dirs/mod.nu"),
-        ),
     ];
 
     for (filename, std_subdir_name, content) in std_submodules.drain(..) {
@@ -87,14 +81,6 @@ pub fn load_standard_library(
         let source = r#"
 # Prelude
 use std/core *
-use std/deprecated_dirs [
-    enter
-    shells
-    g
-    n
-    p
-    dexit
-]
 "#;
 
         // Add a placeholder file to the stack of files being evaluated.