[FIX] fix compile issue on win32 systems

This pull request fixes a weird compile issue on windows that only occurs when building not in unity build mode. With this the error was not observable in the nightly windows builds. Error is

```
2>OpenMS.lib(OpenMS.dll) : error LNK2005: "public: __cdecl std::vector<class OpenMS::Feature,class std::allocator<class OpenMS::Feature> >::~vector<class OpenMS::Feature,class std::allocator<class OpenMS::Feature> >(void)" (??1?$vector@VFeature@OpenMS@@V?$allocator@VFeature@OpenMS@@@std@@@std@@QEAA@XZ) already defined in FeatureFinderAlgorithmSHCtrl.obj
2>OpenMS.lib(OpenMS.dll) : error LNK2005: "public: void __cdecl std::vector<class OpenMS::Feature,class std::allocator<class OpenMS::Feature> >::push_back(class OpenMS::Feature const &)" (?push_back@?$vector@VFeature@OpenMS@@V?$allocator@VFeature@OpenMS@@@std@@@std@@QEAAXAEBVFeature@OpenMS@@@Z) already defined in FeatureFinderAlgorithmSHCtrl.obj
2>OpenMS.lib(OpenMS.dll) : error LNK2005: "public: unsigned __int64 __cdecl std::vector<class OpenMS::Feature,class std::allocator<class OpenMS::Feature> >::size(void)const " (?size@?$vector@VFeature@OpenMS@@V?$allocator@VFeature@OpenMS@@@std@@@std@@QEBA_KXZ) already defined in FeatureFinderAlgorithmSHCtrl.obj
```

The only solution I found was to remove the default instance from `FeatureFinderAlgorithmSH.cpp`.