JIT: remove unused flag.

Source/Core/Core/PowerPC/Jit64/Jit.cpp

@@ -173,7 +173,6 @@ bool Jit64::HandleFault(uintptr_t access_address, SContext* ctx)
 
 void Jit64::Init()
 {
-	jo.optimizeStack = true;
 	EnableBlockLink();
 
 	jo.optimizeGatherPipe = true;

Source/Core/Core/PowerPC/Jit64IL/JitIL.cpp

@@ -243,7 +243,6 @@ namespace JitILProfiler
 
 void JitIL::Init()
 {
-	jo.optimizeStack = true;
 	EnableBlockLink();
 
 	jo.optimizeGatherPipe = true;

Source/Core/Core/PowerPC/JitCommon/JitBase.h

@@ -60,7 +60,6 @@ class JitBase : public CPUCoreBase
 protected:
 	struct JitOptions
 	{
-		bool optimizeStack;
 		bool enableBlocklink;
 		bool optimizeGatherPipe;
 		bool accurateSinglePrecision;