Fix comparison of "numpy" and "pil" types in Image

[BioGeek]

The line

elif self.type == "numpy" or "pil":

is interpreted as

elif (self.type == "numpy") or ("pil"):

where ("pil") is always evaluated as True. See https://stackoverflow.com/a/20002504/50065 for more info.

The reason this wasn't caught by the tests is because they were written like:

  with self.assertRaises(ValueError):
      wrong_type = gr.inputs.Image(type="unknown")
      wrong_type.preprocess(img)
      wrong_type.serialize("test/test_files/bus.png", False)

The line wrong_type.preprocess(img) would trigger a ValueError and the test would be markes as succeeded, but it obscures that the line wrong_type.serialize("test/test_files/bus.png", False) would fail with:

Traceback (most recent call last):
  File "/home/biogeek/github/gradio/test/test_inputs.py", line 320, in test_as_component
    wrong_type.serialize("test/test_files/bus.png", False)
  File "/home/biogeek/github/gradio/gradio/inputs.py", line 768, in serialize
    "."+fmt.lower() if fmt is not None else ".png"))
AttributeError: 'builtin_function_or_method' object has no attribute 'lower'

[height]

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[abidlabs]

Thank you so much @BioGeek for spotting this and explaining the fix. LGTM