Fix test name in test_ctypes.test_errno

[aisk]

This function is actually testing get_last_error() instead of GetLastError(), which is also a valid Windows API but have different behaviors. Although this is not really a problem, I think it's better to make the test code clearer.

[aisk]

Sorry, I read the document in ctypes module again:

The use_last_error parameter, when set to true, enables the same mechanism for the Windows error code which is managed by the GetLastError() and SetLastError() Windows API functions; ctypes.get_last_error() and ctypes.set_last_error() are used to request and change the ctypes private copy of the windows error code.

And found that the ctypes.get_last_error() just wrappers around Windows API GetLastError, so the test name is correct.