Annoying TensorFlow messages

[osma]

I've seen these for a long time but just ignored them. However, I think these messages should not be shown to the user:

2023-07-25 11:31:43.949391: I tensorflow/core/platform/cpu_feature_guard.cc:193] This TensorFlow binary is optimized with oneAPI Deep Neural Network Library (oneDNN) to use the following CPU instructions in performance-critical operations:  AVX2 AVX512F AVX512_VNNI FMA
To enable them in other operations, rebuild TensorFlow with the appropriate compiler flags.
2023-07-25 11:31:44.032688: I tensorflow/core/util/port.cc:104] oneDNN custom operations are on. You may see slightly different numerical results due to floating-point round-off errors from different computation orders. To turn them off, set the environment variable `TF_ENABLE_ONEDNN_OPTS=0`.

The messages are shown for most Annif commands (e.g. annif suggest, annif eval) whenever TensorFlow is installed, even without having configured any projects using the nn_ensemble backend.