Fix invalid aria attributes in material dropdown select.

PiperOrigin-RevId: 205317442

Author: cissyshi

lib/material_select/dropdown_button.html

@@ -16,7 +16,6 @@
      [disabled]="disabled"
      [role]="ariaRole"
      [attr.aria-haspopup]="popupType"
-     aria-autocomplete="none"
      [attr.aria-owns]="ariaOwns"
      [attr.aria-expanded]="ariaExpanded"
      [attr.aria-activedescendant]="ariaActiveDescendant">

lib/material_select/material_dropdown_select.html

@@ -22,8 +22,9 @@
     (trigger)="handleClick($event)"
     popupSource
     #source="popupSource"
+    initPopupAriaAttributes="false"
     popupType="listbox"
-    [ariaOwns]="listId"
+    [ariaOwns]="visible ? listId : null"
     [ariaExpanded]="visible">
   &ngsp;<ng-content select="[buttonContent]"></ng-content>
 </dropdown-button>