Simplify debates and proposals feed layout

Using the `:only-child` selector we can adjust widths with CSS and don't
have to rely on methods calculating which features are available.

app/assets/stylesheets/widgets/feeds/participation.scss

@@ -0,0 +1,20 @@
+.feeds-participation {
+
+  .feed-debates,
+  .feed-proposals {
+    @include grid-col;
+    margin-top: $line-height;
+  }
+
+  .feed-proposals:not(:only-child) {
+    @include breakpoint(medium) {
+      width: 2 * 100% / 3;
+    }
+  }
+
+  .feed-debates:not(:only-child) {
+    @include breakpoint(medium) {
+      width: 1 * 100% / 3;
+    }
+  }
+}

app/components/widgets/feeds/debates_component.html.erb

@@ -1,5 +1,4 @@
-<div id="feed_debates" class="small-12 column margin-top
+<div id="feed_debates" class="feed-debates">
-                              <%= "medium-4" if feed_debates_and_proposals_enabled? %>">
   <div class="feed-content" data-equalizer-watch>
     <h3 class="title"><%= t("welcome.feed.most_active.#{feed.kind}") %></h3>
 

app/components/widgets/feeds/debates_component.rb

@@ -1,5 +1,4 @@
 class Widgets::Feeds::DebatesComponent < ApplicationComponent
-  include FeedsHelper
   attr_reader :feed
 
   def initialize(feed)

app/components/widgets/feeds/proposals_component.html.erb

@@ -1,5 +1,4 @@
-<div id="feed_proposals" class="feed-proposals small-12 column margin-top
+<div id="feed_proposals" class="feed-proposals">
-                                <%= "medium-8" if feed_debates_and_proposals_enabled? %>">
   <div class="feed-content" data-equalizer-watch>
     <h3 class="title"><%= t("welcome.feed.most_active.#{feed.kind}") %></h3>
 

app/components/widgets/feeds/proposals_component.rb

@@ -1,5 +1,4 @@
 class Widgets::Feeds::ProposalsComponent < ApplicationComponent
-  include FeedsHelper
   attr_reader :feed
 
   def initialize(feed)

app/helpers/feeds_helper.rb

@@ -3,19 +3,7 @@ module FeedsHelper
     feed.kind == "processes"
   end
 
-  def feed_debates_enabled?
-    Setting["homepage.widgets.feeds.debates"].present?
-  end
-
-  def feed_proposals_enabled?
-    Setting["homepage.widgets.feeds.proposals"].present?
-  end
-
   def feed_processes_enabled?
     Setting["homepage.widgets.feeds.processes"].present?
   end
-
-  def feed_debates_and_proposals_enabled?
-    feed_debates_enabled? && feed_proposals_enabled?
-  end
 end

spec/system/admin/homepage/homepage_spec.rb

@@ -92,9 +92,6 @@ describe "Homepage", :admin do
         expect(page).to have_content "Most active debates"
         expect(page).to have_css(".debate", count: 3)
       end
-
-      expect(page).to have_css("#feed_proposals.medium-8")
-      expect(page).to have_css("#feed_debates.medium-4")
     end
 
     scenario "Processes", :js do