Prevent incorrect usage of `tracking_attrs` helper

What does this MR do and why?

Related to #348968 (closed)

On !76305 (comment 784820865) we discussed how to merge data-attributes with the tracking_attrs helper, and we introduced a new tracking_attrs_data. This MR:

• Removes unneeded Rails.env.production? guard.
• Adds documentation for tracking_attrs_data variant.
• Updates related specs.

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