Add type hint for LOAD_TRUNCATED_IMAGES

[bencevans]

Changes proposed in this pull request:

• Adds a type hint for ImageFile.LOAD_TRUNCATED_IMAGES.

  Sets the type to bool, otherwise Literal[False] is assumed causing a lint error when setting ImageFile.LOAD_TRUNCATED_IMAGES = True.

[radarhere]

Hi. What environment were you in when you saw the error? Believe it or not, here's what I already see with Pillow 12.0.0 in PyCharm.

[bencevans]

Hi! Ah this will teach me for trying out new toys haha. I'm using ty in VS Code. It's interesting it's picked up as a Literal, it seems stricter than other type checkers.

Forgot to include in the original message but also using pillow===12.0.0.

[radarhere]

Thanks. I can verify that your fix does satisfy ty.

While the change you've suggested here is minor, I expect there will be other ty problems lurking. I'm somewhat hesitant about trying to satisfy multiple type checkers at once, particularly when ty is still in beta.