remove an assert from an attempt to silence clang's false warning

http://llvm.org/bugs/show_bug.cgi?id=12459
It is not clear to me why the explicit cast was there in the first
place, but removing it probably can't make the situation worse
than aborting incorrectly.

framework/source/classes/menumanager.cxx

@@ -146,14 +146,7 @@ MenuManager::MenuManager(
     m_xFrame            = rFrame;
     m_bInitialized      = sal_False;
     m_bIsBookmarkMenu   = sal_False;
-#ifdef LIBO_WERROR
-    // Wtf? Clang says: call to pure virtual member function
-    // 'acquire'; overrides of 'acquire' in subclasses are not
-    // available in the constructor of 'XInterface'
-    assert(!"Call to pure virtual member function");
-#else
-    SAL_STATIC_CAST( ::com::sun::star::uno::XInterface*, (OWeakObject*)this )->acquire();
-#endif
+    acquire();
     const StyleSettings& rSettings = Application::GetSettings().GetStyleSettings();
     m_bShowMenuImages   = rSettings.GetUseImagesInMenus();