Fixes #13093 - Erroneous example in 'touch' help (#13095)

# Description

Fixes #13093 by:

* Removing the mentioned help example
* Updating the `--accessed` and `--modified` flag descriptions to remove
mention of "timestamp/date"

# User-Facing Changes

Help changes

# Tests + Formatting

- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

crates/nu-command/src/filesystem/touch.rs

@@ -35,12 +35,12 @@ impl Command for Touch {
             )
             .switch(
                 "modified",
-                "change the modification time of the file or directory. If no timestamp, date or reference file/directory is given, the current time is used",
+                "change the modification time of the file or directory. If no reference file/directory is given, the current time is used",
                 Some('m'),
             )
             .switch(
                 "access",
-                "change the access time of the file or directory. If no timestamp, date or reference file/directory is given, the current time is used",
+                "change the access time of the file or directory. If no reference file/directory is given, the current time is used",
                 Some('a'),
             )
             .switch(
@@ -189,11 +189,6 @@ impl Command for Touch {
                 example: r#"touch -m -r fixture.json d e"#,
                 result: None,
             },
-            Example {
-                description: r#"Changes the last accessed time of "fixture.json" to a date"#,
-                example: r#"touch -a -d "August 24, 2019; 12:30:30" fixture.json"#,
-                result: None,
-            },
         ]
     }
 }