Remove now-unused kIllegalBytecode bailout reason.

src/bailout-reason.h

Index: src/bailout-reason.h
diff --git a/src/bailout-reason.h b/src/bailout-reason.h
index b3d2c12c28e91de2ea7a59aae293e9be32e9e817..0868cb2757f33d13e30ad272365816536ce51be1 100644
--- a/src/bailout-reason.h
+++ b/src/bailout-reason.h
@@ -91,7 +91,6 @@ namespace internal {
   V(kGraphBuildingFailed, "Optimized graph construction failed")               \
   V(kHeapNumberMapRegisterClobbered, "HeapNumberMap register clobbered")       \
   V(kHydrogenFilter, "Optimization disabled by filter")                        \
-  V(kIllegalBytecode, "Illegal bytecode")                                      \
   V(kImportDeclaration, "Import declaration")                                  \
   V(kIndexIsNegative, "Index is negative")                                     \
   V(kIndexIsTooLarge, "Index is too large")                                    \