[fpdf2] add compatibility with fpdf2 2.7.6

[mschoettle]

Release Notes: https://github.com/py-pdf/fpdf2/blob/master/CHANGELOG.md#276---2023-10-11

Changes txt to text and brings all the other stubs up to date.

I am wondering whether it would be better to add text as an additional argument instead?

This PR currently only covers what's listed in the "Deprecated" section of the release notes. It does not cover the new method text_columns (https://py-pdf.github.io/fpdf2/TextColumns.html). Let me know if this should be added as well at the same time.

Closes #10609

[mschoettle]

The pipeline answered the above question for me :)

[AlexWaygood]

For entirely new modules which are missing from the stub, mypy's stubgen tool can be pretty useful for generating baseline stubs

[mschoettle]

I completed bringing the stubs up to date with v2.7.6. I used mypy's stubgen tool and compared the two versions. There's one place where I replaced Number first with int | float and then float due to a violation. I left a TODO there.

[srittau]

Thanks! A few things I noticed below.

[srittau]

@mschoettle Just using float seems to work fine. I suggest we don't use Number.

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[mschoettle]

@srittau Thanks a lot for fixing the weird Number issue!