Remove superfluous datefield props

Fixes #7397

src/Forms/DateField.php

@@ -72,13 +72,6 @@ class DateField extends TextField
      */
     protected $dateFormat = null;
 
-    /**
-     * Set if js calendar should popup
-     *
-     * @var bool
-     */
-    protected $showCalendar = false;
-
     /**
      * Length of this date (full, short, etc).
      *
@@ -87,13 +80,6 @@ class DateField extends TextField
      */
     protected $dateLength = null;
 
-    /**
-     * Override locale for client side.
-     *
-     * @var string
-     */
-    protected $clientLocale = null;
-
     protected $inputType = 'date';
 
     /**