Revert: Do not allow exceptions in Cursor destructor (#585)

We need to report errors in destructors, apparently.  Otherwise all tests fail and we get a
segfault!  I need to look into this more.

src/cursor.cpp

@@ -458,10 +458,6 @@ static void Cursor_dealloc(Cursor* cursor)
     if (Cursor_Validate((PyObject*)cursor, CURSOR_REQUIRE_CNXN))
     {
         closeimpl(cursor);
-        if (PyErr_Occurred()) {
-            // We are in a Cursor destructor (__del__) and should not raise exceptions.
-            PyErr_Clear();
-        }
     }
     Py_XDECREF(cursor->inputsizes);
     PyObject_Del(cursor);