FIX: Recalculate scores only when approving or transitioning to pending. (#13009)

Recalculating a ReviewableFlaggedPost's score after rejecting or ignoring it sets the score as 0, which means that we can't find them after reviewing. They don't surpass the minimum priority threshold and are hidden.

Additionally, we only want to use agreed flags when calculating the different priority thresholds.

app/models/reviewable.rb

@@ -175,7 +175,13 @@ class Reviewable < ActiveRecord::Base
         reviewable.save!
       else
         reviewable = find_by(target: target)
-        reviewable.log_history(:transitioned, created_by) if old_status != statuses[:pending]
+
+        if old_status != statuses[:pending]
+          # If we're transitioning back from reviewed to pending, we should recalculate
+          # the score to prevent posts from being hidden.
+          reviewable.recalculate_score
+          reviewable.log_history(:transitioned, created_by)
+        end
       end
     end
 
@@ -584,8 +590,6 @@ class Reviewable < ActiveRecord::Base
     SQL
   end
 
-protected
-
   def recalculate_score
     # pending/agreed scores count
     sql = <<~SQL
@@ -633,6 +637,8 @@ protected
     self.score
   end
 
+protected
+
   def increment_version!(version = nil)
     version_result = nil