fix debug build on s390

... by removing obsolete OSL_ENSURE. nVtableCall was renamed to
nFunctionIndex and the same check is done a couple of lines above.

Change-Id: Id52b69adceb337049c50a599aefc718498d688c0

bridges/source/cpp_uno/gcc3_linux_s390/cpp2uno.cxx

@@ -354,7 +354,6 @@ static typelib_TypeClass cpp_mediate(
     }
 
     // determine called method
-    OSL_ENSURE( nVtableCall < pTypeDescr->nMapFunctionIndexToMemberIndex, "### illegal vtable index!" );
     sal_Int32 nMemberPos = pTypeDescr->pMapFunctionIndexToMemberIndex[nFunctionIndex];
     OSL_ENSURE( nMemberPos < pTypeDescr->nAllMembers, "### illegal member index!" );