Post Terms: Remove unnecessary 'get_the_terms' call

[Mamaduka]

What?

PR updates the Post Terms render callback and removes unnecessary get_the_terms call.

Why?

The post terms are retrieved, but values are never used for rendering. The get_the_term_list handles the markup and internally calls the get_the_terms function.

Testing Instructions

1. Open a post or page.
2. Insert a Post Term block - Tags or Categories.
3. Preview the post. Confirm it renders nothing.
4. Assign a term to a post and preview it again.
5. Confirm the correct term list is rendered.

Testing Instructions for Keyboard

Same.

Screenshots or screencast

[github-actions]

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Co-authored-by: Mamaduka <[email protected]>
Co-authored-by: aristath <[email protected]>

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[aristath]

LGTM 👍

[Mamaduka]

Thank you, @aristath!