Minor IGraphicBufferProducer cleanup changes.

We have removed references of IGraphicBufferProducer outside of libgui
so this include is no longer necessary. More information at
go/warren-buffers.

Bug: 342197851
Test: build and run
Flag: com.android.graphics.libgui.flags.wb_platform_api_improvements
Change-Id: I1dba80493523ad553ae1b61cb135bf2e824d60b7