Fix proposal supports query

Proposal supports query was returning the supports received for each
group. Now it returns the supports received for the given group.

app/services/proposal_supports_query.rb

@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 class ProposalSupportsQuery
   attr_reader :params
 
@@ -18,6 +16,12 @@ class ProposalSupportsQuery
       grouped_votes[group] = votes.inject(0) { |sum, vote| sum + vote.vote_weight }
     end
 
+    accumulated = 0
+    grouped_votes.each do |k, v|
+      accumulated += v
+      grouped_votes[k] = accumulated
+    end
+
     grouped_votes
   end