Tensorflow requirements

[stweil]

Is the current limitation which only allows tensorflow 2.5.0 really necessary? Why not 2.5.1, 2.6 or even the very latest tensorflow?

Such old versions of Tensorflow are for example not provided for Python 3.10 (which only supports tensorflow 2.8.0), and even for Python 3.7 and other Python versions it causes version conflicts with other packages which are required for OCR-D.

[crater2150]

As explained in #5, having dynamic dependencies broke the installation recently, and I don't have time to regularly check versions of all transitive dependencies. If you can test installation with newer versions, I'll accept PRs updating the requirements file.