K/N custom-alloc: Fix GC stats for NextFitPage ^KT-55364

Swept and kept objects in NextFitPages are double counted; first in
GCApi::SweepObject and then again inside NextFitPage::Sweep. This fix
removes the latter.


Co-authored-by: Troels Lund <troels@google.com>

Merge-request: KOTLIN-MR-691
Merged-by: Alexander Shabalin <alexander.shabalin@jetbrains.com>

kotlin-native/runtime/src/custom_alloc/cpp/NextFitPage.cpp

@@ -47,10 +47,8 @@ bool NextFitPage::Sweep(GCSweepScope& sweepHandle, FinalizerQueue& finalizerQueu
         if (block->isAllocated_) {
             if (SweepObject(block->data_, finalizerQueue, sweepHandle)) {
                 alive = true;
-                sweepHandle.addKeptObject();
             } else {
                 block->Deallocate();
-                sweepHandle.addSweptObject();
             }
         }
     }