[MaterialTimePicker][a11y] Fixing the Talkback focusability of the "Select time" label on the time picker component.

PiperOrigin-RevId: 729257174

Author: Material Design Team

lib/java/com/google/android/material/timepicker/res/layout/material_timepicker_dialog.xml

@@ -30,7 +30,7 @@
     android:layout_height="wrap_content"
     android:layout_marginTop="16dp"
     android:layout_marginStart="24dp"
-    android:importantForAccessibility="no"
+    android:importantForAccessibility="yes"
     android:text="@string/material_timepicker_select_time"
     app:layout_constraintStart_toStartOf="parent"
     app:layout_constraintTop_toTopOf="parent" />