improved log msg

..because actually we don't know if the intention is
to drop those waste elements -- and for sure this
discarding of waste does not happen through the
invocation logged here; rather it happens by
abandoning the scope

src/lib/diff/test-mutation-target.hpp

@@ -285,7 +285,7 @@ namespace diff{
       void
       logScopeCompletion (iterator processingPos)
         {
-          log_.event ("completeScope", _Fmt{"⤴ scope%s completed / %d waste elm(s) dropped"}
+          log_.event ("completeScope", _Fmt{"⤴ scope%s completed / %d waste elm(s)"}
                                        % (processingPos? " NOT":"")
                                        % prev_content_.size());
         }