tests/io/bytesio_ext2: Remove dependency on specific EINVAL value

If MICROPY_USE_INTERNAL_ERRNO is disabled, MP_EINVAL is not guaranteed
to have the value 22, so we cannot depend on OSError(22,).
Instead, to support any given port's errno values, without relying
on uerrno, we just check that the args[0] is positive.

tests/io/bytesio_ext2.py

@@ -10,4 +10,4 @@ except Exception as e:
     # CPython throws ValueError, but MicroPython has consistent stream
     # interface, so BytesIO raises the same error as a real file, which
     # is OSError(EINVAL).
-    print(repr(e))
+    print(type(e), e.args[0] > 0)

tests/io/bytesio_ext2.py.exp

-OSError(22,)
+<class 'OSError'> True