[RLlib] Enable complex action spaces with stateful modules.

[simonsays1980]

Why are these changes needed?

Stateful modules add a time dimension to tensors which cannot be handles by complex action distributions so far due to a dimension mismatch. This PR intends to fix this bug and therewith enable complex action spaces with stateful modules.

Related issue number

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• Testing Strategy
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  • This PR is not tested :(

[sven1977]

LGTM! Thanks for the fix @simonsays1980