opengl dr.memory: Avoid double delete.

The context is deleted via OpenGLSalGraphicsImpl::~OpenGLSalGraphicsImpl later,
doing it already here leads to a double delete and a crash.

Change-Id: Icf1bed81501b5ac67ef60901eaa73e5ee5540a9f

vcl/source/app/svmain.cxx

@@ -442,15 +442,6 @@ void DeInitVCL()
     }
     if ( pSVData->mpDefaultWin )
     {
-        OpenGLContext* pContext = pSVData->mpDefaultWin->GetGraphics()->GetOpenGLContext();
-        if( pContext )
-        {
-#ifdef DBG_UTIL
-            pContext->DeRef(NULL);
-#else
-            pContext->DeRef();
-#endif
-        }
         delete pSVData->mpDefaultWin;
         pSVData->mpDefaultWin = NULL;
     }