[Docs]: Fix Audio icon.

SearchChipViewManager relies on specific order of Mime types when
fetching an icon:
IconUtils.loadMimeIcon(context, chipData.getMimeTypes()[0]);
Thus we must not sort them. To support equals, we use set comparison to
avoid order of MIME types resulting in inequality.

Bug: 430803032
Test: atest DocumentsUIUnitTests
Flag: com.android.documentsui.flags.use_material3
Change-Id: I37c63709beda7b5ce2670170129d669d13734989