Revert heap growth multiplier logic for Generational CC collection.

Have Generational and Non-Generational CC collections both use
Heap::HeapGrowthMultiplier directly in Heap::GrowForUtilization.

Test: ART run-tests & gtests, libcore tests, JDWP tests (host & device)
Test: Device/emulator boot test
Bug: 67628039
Bug: 12687968
Change-Id: Ie4b8aa9dc190ed8a9d069b2dc957c50e7a0ef05a
diff --git a/runtime/gc/heap.cc b/runtime/gc/heap.cc
index 56751cc..1578db5 100644
--- a/runtime/gc/heap.cc
+++ b/runtime/gc/heap.cc
@@ -3492,8 +3492,8 @@
   uint64_t target_size;
   collector::GcType gc_type = collector_ran->GetGcType();
   // Use the multiplier to grow more for foreground.
-  const double multiplier =
-      HeapGrowthMultiplier() + (kEnableGenerationalConcurrentCopyingCollection ? 3.0 : 0.0);
+  const double multiplier = HeapGrowthMultiplier();  // Use the multiplier to grow more for
+  // foreground.
   const uint64_t adjusted_min_free = static_cast<uint64_t>(min_free_ * multiplier);
   const uint64_t adjusted_max_free = static_cast<uint64_t>(max_free_ * multiplier);
   if (gc_type != collector::kGcTypeSticky) {