Hide recent searches as part of M3 uplift.

On larger screens the searchbar will be displayed inside the toolbar but
currently the M3 components library doesn't have DockedSearchBar which
supports a drop down for recent searches. And a full screen drop down is
not a great UX.

To make the user experience consistent, this will hide recent searches
on all form factors until DockedSearchBar is available.

Bug: 404388986
Flag: com.android.documentsui.flags.use_material3
Test: test DocumentsUIGoogleTests:com.android.documentsui.SearchViewUiTest
Change-Id: Ib8c4fe21d1441e174d119a689dcfb00af827a36d