AOTIR: Stop passing a mutex around. It's already guarded

Source/Tools/FEXLoader/IRLoader.cpp

@@ -158,9 +158,8 @@ class DummySyscallHandler: public FEXCore::HLE::SyscallHandler, public FEXCore::
   }
 
   // These are no-ops implementations of the SyscallHandler API
-  std::shared_mutex StubMutex;
   FEXCore::HLE::AOTIRCacheEntryLookupResult LookupAOTIRCacheEntry(uint64_t GuestAddr) override {
-    return {0, 0, FHU::ScopedSignalMaskWithSharedLock {StubMutex}};
+    return {0, 0};
   }
 };