posts: show only last successful flag on deleted posts.

In the "This post was deleted" notice, show only the last successful
flag, instead of all previous flags (which may include rejected flags).

app/views/posts/partials/show/_notices.html.erb

@@ -25,9 +25,9 @@
   </div>
 <% elsif post.is_deleted? %>
   <div class="notice notice-small post-notice post-notice-deleted">
-    <% if post.flags.any? %>
-      <p>This post was deleted for the following reasons: </p>
-      <%= render "post_flags/reasons", flags: post.flags %>
+    <% if post.flags.succeeded.last.present? %>
+      <p>This post was deleted for the following reason: </p>
+      <%= render "post_flags/reasons", flag: post.flags.succeeded.last %>
     <% else %>
       <p>This post was deleted</p>
     <% end %>

test/functional/posts_controller_test.rb

@@ -540,6 +540,15 @@ class PostsControllerTest < ActionDispatch::IntegrationTest
         end
       end
 
+      context "a deleted post" do
+        should "render" do
+          @post.delete!("no", user: @user)
+          get post_path(@post)
+
+          assert_response :success
+        end
+      end
+
       context "with pools" do
         should "render the pool list" do
           as(@user) { @post.update(tag_string: "newpool:comic") }