enable/update some example tests so they work again (#10058)

# Description

This PR updates some `Example` tests so that they work again. The only
one I couldn't figure out is the one in the `filter` command. It should
work but does not. However, I left the test in because it's valuable, it
just has a `None` result. I'd like to fix this but I'm not sure how.

# User-Facing Changes
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# Tests + Formatting
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crates/nu-command/src/platform/sleep.rs

@@ -78,16 +78,16 @@ impl Command for Sleep {
                     span: Span::test_data(),
                 }),
             },
-            // Example {
-            //     description: "Sleep for 3sec",
-            //     example: "sleep 1sec 1sec 1sec",
-            //     result: None,
-            // },
-            // Example {
-            //     description: "Send output after 1sec",
-            //     example: "sleep 1sec; echo done",
-            //     result: None,
-            // },
+            Example {
+                description: "Sleep for 3sec",
+                example: "sleep 1sec 1sec 1sec",
+                result: None,
+            },
+            Example {
+                description: "Send output after 1sec",
+                example: "sleep 1sec; echo done",
+                result: None,
+            },
         ]
     }
 }