Refine exit command documentation to remove optional exit status details and clarify termination behavior

Author: andy1li

stage_descriptions/base-04-pn5.md

@@ -4,13 +4,7 @@ In this stage, you'll implement the `exit` builtin.
 
 The [`exit`](https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#exit) builtin is a special command that terminates the shell.
 
-It takes an optional numeric argument as the shell's [exit status](https://en.wikipedia.org/wiki/Exit_status):
-```bash
-$ exit 0    # Exit with status 0 (success)
-$ exit 1    # Exit with status 1 (error)
-```
-
-When your shell receives the `exit` command, it should terminate immediately with the specified exit code.
+When your shell receives the `exit` command, it should terminate immediately.
 
 ### Tests
 
@@ -25,13 +19,7 @@ It will then send an invalid command to your shell, followed by the `exit` comma
 ```bash
 $ invalid_command_1
 invalid_command_1: command not found
-$ exit 0
+$ exit
 ```
 
-The tester will verify that:
-- Your shell terminates after receiving the `exit` command
-- Your shell exits with status code `0`
-
-### Notes
-
-- The tester will always pass in `0` as the argument to the `exit` command.
+The tester will verify that your shell terminates after receiving the `exit` command.