Fix incorrect [enabled] documentation (#161650)

This PR updates the documentation to align with the current behavior of
the InputDecorator. When [enabled] is false, [helperText],[errorText],
and [counterText] are actually still displayed. So, this updates the
docs to align with current functionality.

Fixes #161602

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---------

Co-authored-by: Mitchell Goodwin <58190796+MitchellGoodwin@users.noreply.github.com>

packages/flutter/lib/src/material/input_decorator.dart

@@ -3696,8 +3696,7 @@ class InputDecoration {
   ///    rounded rectangle around the input decorator's container.
   final InputBorder? border;
 
-  /// If false [helperText],[errorText], and [counterText] are not displayed,
-  /// and the opacity of the remaining visual elements is reduced.
+  /// If false the opacity of the visual elements is reduced, including [helperText],[errorText], and [counterText].
   ///
   /// This property is true by default.
   final bool enabled;