Revert "progress-bar: re-draw last update if nothing new for 1sec."

Not ready for this yet, causes the prompt to disappear in nix repl
and more generally can overwrite non-progress-bar messages.

This reverts commit 44de71a396.

src/nix/progress-bar.cc

@@ -75,9 +75,8 @@ public:
         updateThread = std::thread([&]() {
             auto state(state_.lock());
             while (state->active) {
-                auto r = state.wait_for(updateCV, std::chrono::seconds(1));
+                state.wait(updateCV);
                 draw(*state);
-                if (r == std::cv_status::no_timeout)
                 state.wait_for(quitCV, std::chrono::milliseconds(50));
             }
         });