Apply Performance/CompareWithBlock rule to sort!

We should have applied this change in commit a78a8d592, since it was
added in rubocop-performance 1.18.0, but forgot to do so.

app/helpers/officing_helper.rb

@@ -4,7 +4,7 @@ module OfficingHelper
     officer_assignments.each do |oa|
       options << [oa.booth_assignment.booth.name.to_s, oa.id]
     end
-    options.sort! { |x, y| x[0] <=> y[0] }
+    options.sort_by! { |x| x[0] }
     options_for_select(options, params[:oa])
   end