Enabled PolicyStd logging for gaussian_sac

[s8phsaue]

Description

Small change, we now check if the actor_type is either 'gaussian_learning' or 'gaussian_sac' when deciding on logging Train/PolicyStd.

Motivation and Context

When I tried to run CPO with 'gaussian_sac' as the underlying actor_type, the following assertion triggered:

AssertionError: Key Train/PolicyStd has not been registered

Upon investigation, I noticed that the abovementioned key gets added to the logger only if the actor_type is 'gaussian_learning'.

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds core functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• I have read the CONTRIBUTION guide. (required)
• My change requires a change to the documentation.
• I have updated the tests accordingly. (required for a bug fix or a new feature)
• I have updated the documentation accordingly.
• I have reformatted the code using make format. (required)
• I have checked the code using make lint. (required)
• I have ensured make test pass. (required)