(Re)move OBC-GDPR-ULT instructions from the translation?

originally brought up in https://github.com/con/open-brain-consent/issues/51#issuecomment-633481776 . @mhavu mentioned that there are instructions which are not "participant-oriented" which are included in the GDPR-ULT: https://open-brain-consent.readthedocs.io/en/latest/gdpr/ultimate_gdpr.html#instructions and its translations. But none of the "instructions" in other documents is included in the translations.
It seems that the included GDPR-ULT instructions are generic, and some are even applicable to the OBC-ULT as well (on all the `[]` and `<>` fields). They are useful to convey to the user of the consent form(s) but indeed not targeting participants.
ATM all GDPR-ULT include those instructions translated, so it would be kinda a waste to just strip they away, so may be we would like to move them somewhere.

Start with the GDPR-ULT instructions section in the Read the Docs page and compare it with the translated GDPR-ULT documents. Review the discussion in issue 51 to understand the participant-oriented distinction and identify where the reusable instructions should live. Done means the instructions have an agreed location, translations remain useful, and the affected documentation links or references are updated.

Written by the indexing model from the issue text.