RFR: Remove leftover include in C2

[Roman Kennke]

This is not needed anymore, as of today's Roland's improvements:

Ok?

Roman

diff --git a/src/hotspot/share/opto/loopopts.cpp
b/src/hotspot/share/opto/loopopts.cpp
--- a/src/hotspot/share/opto/loopopts.cpp
+++ b/src/hotspot/share/opto/loopopts.cpp
@@ -44,9 +44,6 @@
 #if INCLUDE_ZGC
 #include "gc/z/c2/zBarrierSetC2.hpp"
 #endif
-#if INCLUDE_SHENANDOAHGC
-#include "gc/shenandoah/c2/shenandoahBarrierSetC2.hpp"
-#endif

 //=============================================================================
 //------------------------------split_thru_phi---------------------------------