Update TW for docs guidelines

Why is this change being made?

• For gitlab-org/technical-writing#123 (closed)
• TW handbook: Mike Lewis
• Docs guidelines: Mike Lewis

Does this MR meet the acceptance criteria?

Assign to DRI

• Did you assign this change to the correct DRI of the page or information you are changing?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what