cppu::OMultiTypeInterfaceContainerHelperVar hashImpl param is unused

...since f059134fab0f91b7a15594ad06536a13fbfae034 "INTEGRATION: CWS
cppuhelpshrink: #i72766# save memory in cppuhelper, using a vector instead of a
hash_map" (but a dummy "void" default is left in place for backwards
compatibility).

Change-Id: I3bb0af8158f34737d41c344464f3cf944e2891ed