Parse QR Code declared a `checks` regex that matched any JPEG, PNG,
GIF, WEBP or BMP magic bytes. Magic aggregates every operation with a
`checks` property and runs them, so any image input triggered a full
QR parse attempt that produced a 'Could not read a QR code from the
image' warning in the browser console for every image, even when no QR
code was present.
There is no cheap way to detect a QR code without attempting a full
parse, so Parse QR Code should not participate in Magic. Users can add
it manually when they know the image contains a QR code.
Adds a regression test asserting Parse QR Code declares no `checks`.
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