OpenNMT-tf 2.27.0

Changes

• Remove support for older TensorFlow versions 2.4 and 2.5
• Remove support for deprecated Python version 3.6

New features

• Support TensorFlow 2.9
• Integrate the new CTranslate2 converter to export more Transformer variants, including multi-features models

Fixes and improvements

• Fix error when loading the SavedModel of Transformer models with relative position representations
• Fix dataset error in inference with language models
• Fix batch size autotuning error with language models
• Fix division by zero error on some systems when the time to the last training log is too small