achieved goals never actually achievable, show up in the list of available goals for feature assignment

as-is:

• features details page. providing as-is & to-be details for a given feature for the team.
• I'm completing the additional information / metadata for the feature. I associate a feature to a goal/multiple goals.
• I click on the goals drop-down list.
• goals I know that are marked "Achieved" are in the dropdown list for me as an option to associate the feature to a goal.
• OUCH. Goals marked “Achieved” still present themselves as candidates for new element association. This is painful and adds clutter.

to-be:

• if we’ve “achieved” the goal, the goal should be hidden from new association into {feature, master feature, requirement, idea, initiative, release} elements. The goal is "achieved"!
• it’s fine to change the goal from “achieved” to {some other status}. Let me declare that adjustment in the goals details (which is do-able today). When (or if) I change the goal from “achieved” to {some other status}, then let it show up as a candidate in the appropriate experience.