Fix typo in budget executions spec

We were expecting the page not to have content which is actually there.
The test passed (most of the time) because before clicking the
"Milestones" link the content was not present, and we checked the page
content before the AJAX request generated by clicking the link had
finished.

spec/features/budgets/executions_spec.rb

@@ -53,7 +53,7 @@ feature "Executions" do
     click_link "See results"
     click_link "Milestones"
 
-    expect(page).not_to have_content("No winner investments in this state")
+    expect(page).to have_content("No winner investments in this state")
 
     select "Executed (0)", from: "status"