Remove state assigning from wxProgressDialog::GetHandle()

This was added in 01bd848eb9 without any
explanation and probably was a copy-and-paste typo as it just doesn't
make any sense to change the state of the dialog in this accessor
function (and if the state doesn't change, then this assignment is just
completely useless).

Remove the apparently unnecessary assignment and also an unnecessary
temporary variable.

src/msw/progdlg.cpp

@@ -576,13 +576,8 @@ WXWidget wxProgressDialog::GetHandle() const
 #ifdef wxHAS_MSW_TASKDIALOG
     if ( HasNativeTaskDialog() )
     {
-        HWND hwnd;
-        {
-            wxCriticalSectionLocker locker(m_sharedData->m_cs);
-            m_sharedData->m_state = m_state;
-            hwnd = m_sharedData->m_hwnd;
-        }
-        return hwnd;
+        wxCriticalSectionLocker locker(m_sharedData->m_cs);
+        return m_sharedData->m_hwnd;
     }
 #endif
     return wxGenericProgressDialog::GetHandle();