Fix Outputs in Hashmap Examples

Closes #60014

GitOrigin-RevId: f2acfde
Change-Id: I4ee330ad5c359bf584e8eeab238a5683957816a3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/406781
Reviewed-by: Slava Egorov <[email protected]>

Author: piedcipher

sdk/lib/collection/hash_map.dart

@@ -83,7 +83,7 @@ typedef _Hasher<K> = int Function(K object);
 /// ```
 /// To remove an entry with a specific key, use [remove].
 /// ```dart continued
-/// final removeValue = planets.remove(5);
+/// final removeValue = planets.remove(6);
 /// print(removeValue); // Jupiter
 /// print(planets); // fx {4: Mars, 3: Earth, 5: Saturn}
 /// ```