fix: Correct an off-by-one-error in lanczos_filter

[72374]

I guess that this does practically not matter, but the function is limited asymmetrically now (which seems incorrect to me) and it does neither match what is currently written for this form of the function on Wikipedia nor the code in image-rs.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[72374]

Feel free to download the commit and apply it yourself. I do not want to read that contract.