Clarify making group retrospectives "public"

Why is this change being made?

There seems to be a lack of clarity around what making a retrospective or notes from a retrospective "public" means. I'm intending this change to clarify what is being asked.

I have included text from the retrospective issue template that seems to suggest that the whole issue should be made public as long as the team agrees in the hope that we can come to some shared understanding of what's being asked.

I believe that removing this confidential flag is in line with our Transparency value, allows people to learn in more detail from other group's retrospectives and, still provides some flexibility to managers in the event that they feel some or all of their group's retrospective should not be shared with GitLab team members.

How will this merge request impact page speed?

No impact.

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