Fix broken fixed point LSTM example

[julianhoever]

The fixed point LSTM example seems to be broken. The class FirmwareENv5 is passed a string, which does not correspond to the constuctor of this class. It must be checked whether the example still works and corrected if necessary.

https://github.com/es-ude/elastic-ai.creator/blob/d07ffc2d64d59fb61de2b3a93448ad71e2f6c53d/elasticai/creator/nn/fixed_point/lstm/example.py