Keras-tuner > 1.0.1 compatibility with tensorflow 2.1.4

In the process of retraining the trackers I found that the keras-tuner used doesn't work with our tensorflow version 2.1.4. Here is the reported bug https://github.com/keras-team/keras-tuner/issues/448. In the mean time I downgraded to keras-tuner 1.0.1. Alternatively we can just update to tf>=2.2, but given that there were other issues when upgrading that require more work (Particularly the reshaping between model size and tile sizes), it might be worth just wait for the eventual Pytorch rework.