Use a button to delete surveys

As mentioned in commit 5311daadf, there are several reasons to use
buttons in these situations. And, as mentioned in the previous commits,
using buttons instead of links for actions requiring confirmation will
help us test for accessibility issues.

app/assets/stylesheets/dashboard.scss

@@ -442,6 +442,14 @@
   .button {
     font-weight: bold;
   }
+
+  button {
+    cursor: pointer;
+
+    &:hover {
+      text-decoration: underline;
+    }
+  }
 }
 
 .community-poll {

app/views/dashboard/polls/_poll.html.erb

@@ -27,10 +27,10 @@
     <% end %>
     <p class="help-text"><%= t("dashboard.polls.poll.show_results_help") %></p>
 
-    <%= link_to t("dashboard.polls.poll.delete"),
-                proposal_dashboard_poll_path(proposal, poll),
-                method: :delete,
-                "data-confirm": t("dashboard.polls.poll.alert_notice"),
-                class: "delete" %>
+    <%= button_to t("dashboard.polls.poll.delete"),
+                  proposal_dashboard_poll_path(proposal, poll),
+                  method: :delete,
+                  "data-confirm": t("dashboard.polls.poll.alert_notice"),
+                  class: "delete" %>
   </div>
 </div>

spec/system/dashboard/polls_spec.rb

@@ -199,7 +199,7 @@ describe "Polls" do
     visit proposal_dashboard_polls_path(proposal)
 
     within("#poll_#{poll.id}") do
-      accept_confirm { click_link "Delete survey" }
+      accept_confirm { click_button "Delete survey" }
     end
 
     expect(page).to have_content("Survey deleted successfully")
@@ -214,7 +214,7 @@ describe "Polls" do
     visit proposal_dashboard_polls_path(proposal)
 
     within("#poll_#{poll.id}") do
-      accept_confirm { click_link "Delete survey" }
+      accept_confirm { click_button "Delete survey" }
     end
 
     expect(page).to have_content("You cannot destroy a survey that has responses")