8371573: Shenandoah: Remove unnecessary include after JDK-8351091

Reviewed-by: wkemper, shade

Author: kdnilsen

src/hotspot/share/gc/shenandoah/shenandoahMarkingContext.cpp

@@ -27,7 +27,6 @@
 #include "gc/shared/markBitMap.inline.hpp"
 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
 #include "gc/shenandoah/shenandoahMarkingContext.hpp"
-#include "shenandoahGlobalGeneration.hpp"
 
 ShenandoahMarkingContext::ShenandoahMarkingContext(MemRegion heap_region, MemRegion bitmap_region, size_t num_regions) :
   _mark_bit_map(heap_region, bitmap_region),