FEATURE: Hide Reviewable scores, change score filter to Priority

We found score hard to understand. It is still there behind the scenes
for sorting purposes, but it is no longer shown.

You can now filter by minimum priority (low, med, high) instead of
score.

lib/flag_query.rb

@@ -173,7 +173,7 @@ module FlagQuery
 
     params = {
       pending: Reviewable.statuses[:pending],
-      min_score: SiteSetting.min_score_default_visibility
+      min_score: Reviewable.min_score_for_priority
     }
 
     results = DB.query(<<~SQL, params)