Refactor: Use IID_IFile constant in test_typeinfo.py.

In `comtypes/test/test_typeinfo.py`, the hardcoded GUID for `IFile`
was replaced with the `IID_IFile` constant to improve readability.

Author: junkmd

comtypes/test/test_typeinfo.py

@@ -89,13 +89,13 @@ def test_TypeInfo(self):
             tlib.GetTypeInfoOfGuid(guid_null)
         self.assertEqual(comtypes.hresult.TYPE_E_ELEMENTNOTFOUND, cm.exception.hresult)
 
-        guid = GUID("{C7C3F5A4-88A3-11D0-ABCB-00A0C90FFFC0}")
-        ti = tlib.GetTypeInfoOfGuid(guid)
+        IID_IFile = GUID("{C7C3F5A4-88A3-11D0-ABCB-00A0C90FFFC0}")
+        ti = tlib.GetTypeInfoOfGuid(IID_IFile)
         c_tlib, c_index = ti.GetContainingTypeLib()
         c_ti = c_tlib.GetTypeInfo(c_index)
         self.assert_tlibattr_equal(c_tlib, tlib)
         self.assertEqual(c_ti, ti)
-        self.assertEqual(guid, ti.GetTypeAttr().guid)
+        self.assertEqual(IID_IFile, ti.GetTypeAttr().guid)
 
 
 class Test_GetModuleFileName(unittest.TestCase):