Set `library_name` to `tf-keras`.

Model 'kobrasoft/kobraspeech-rnn-cs' seems to be compatible only with "Keras 2" and not "Keras 3". To distinguish them, models compatible with legacy Keras 2.x should be tagged as `tf-keras` while models compatible with Keras 3.x are tagged as `keras`.

This PR updates the model card to replace the explicit `library_name: keras` metadata which is now outdated by `library_name: tf-keras`. Updating this metadata will facilitate its discoverability and usage.

For more information about `keras` and `tf-keras` library names, check out this pull request: https://github.com/huggingface/huggingface.js/pull/774.

README.md

@@ -2,7 +2,7 @@
 datasets:
 - mozilla-foundation/common_voice_17_0
 language: cs
-library_name: tensorflow
+library_name: tf-keras
 license: cc-by-nc-sa-4.0
 metrics:
 - wer
@@ -12,7 +12,6 @@ tags:
 - automatic-speech-recognition
 - speech
 - Tensorflow
-- Keras
 - RNN
 model-index:
 - name: KobraSpeech RNN Czech