Revert "LocalStore::addToStoreFromDump copy in chunks"

This reverts commit 592851fb67. We don't
need this extra feature anymore

src/libutil/serialise.hh

@@ -273,19 +273,10 @@ struct ChainSource : Source
 /* Convert a function that feeds data into a Sink into a Source. The
    Source executes the function as a coroutine. */
 std::unique_ptr<Source> sinkToSource(
-    std::function<void(Sink &, size_t &)> fun,
-    std::function<void()> eof = []() {
-        throw EndOfFile("coroutine has finished");
-    });
-
-static inline std::unique_ptr<Source> sinkToSource(
     std::function<void(Sink &)> fun,
     std::function<void()> eof = []() {
         throw EndOfFile("coroutine has finished");
-    })
-{
-    return sinkToSource([fun](Sink & s, size_t & _) { fun(s); }, eof);
-}
+    });
 
 
 void writePadding(size_t len, Sink & sink);