[BUG] Normalisation components being initialised when disabled.

[Siddarth Singh]

Describe the bug

Even if normalization is disabled on_building_init_end will still be called in the normalization components. This creates an error if the datatype of the observation space is not an array as it attempts to set obs_shape based on the shape of the observation space.

To Reproduce

Steps to reproduce the behavior:

1. Run run_ippo.py with normalization disabled using an environment that does not use an array as the observation space.

Expected behavior

If normalization is disabled it should not be initialised.