Remove code that is no longer needed since minSdk for support library is API
14.
This code collapses FloatingActionButtonImpl, FloatingActionButtonGingerbread
and FloatingActionButtonIcs into one class.
Bug: 32794064
Test: ./gradlew clean assemble still works
Change-Id: Id20c0d1807e08ab11ece63883debe2682cfa815f
PiperOrigin-RevId: 151874300