Clarify parameter name in isEmpty documentation

Updated parameter description for isEmpty method.

Author: omkarhole

content/dart/concepts/map/terms/is-empty/is-empty.md

@@ -21,7 +21,8 @@ In Dart, the **`.isEmpty`** property is used to check if a `Map` contains no key
 map.isEmpty
 ```
 
-- `mapName`: The `Map` to be checked.
+- `map`: The `Map` is object.
+- 
 
 ## Example