fix: remove header related docs from date/time picker.

docs/controls/datepicker.md

@@ -7,16 +7,13 @@ The `DatePicker` control allows the user to pick a date value.
 {% tabs %}
 {% tab title="XAML" %}
 ```markup
-<DatePicker Header="Date of birth"/>
+<DatePicker/>
 ```
 {% endtab %}
 
 {% tab title="CS" %}
 ```csharp
-DatePicker birthDatePicker = new DatePicker()
-{
-    Header = "Date of birth"
-};
+DatePicker birthDatePicker = new DatePicker();
 ```
 {% endtab %}
 {% endtabs %}

docs/controls/timepicker.md

@@ -9,14 +9,13 @@ This example shows how to create a simple time picker with a header in XAML or i
 {% tabs %}
 {% tab title="XAML" %}
 ```markup
-<TimePicker Header="Arrival time"/>
+<TimePicker/>
 ```
 {% endtab %}
 
 {% tab title="CS" %}
 ```csharp
 TimePicker arrivalTimePicker = new TimePicker();
-arrivalTimePicker.Header = "Arrival time";
 ```
 {% endtab %}
 {% endtabs %}