Enable RSpec/NotToNot cop and fix all issues

Read about cop at http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/NotToNot

spec/features/admin/site_customization/content_blocks_spec.rb

@@ -23,7 +23,7 @@ feature "Admin custom content blocks" do
         click_link "Custom content blocks"
       end
 
-      expect(page).to_not have_content "footer (es)"
+      expect(page).not_to have_content "footer (es)"
 
       click_link "Create new content block"
 
@@ -90,8 +90,8 @@ feature "Admin custom content blocks" do
 
       click_button "Delete block"
 
-      expect(page).to_not have_content("#{block.name} (#{block.locale})")
-      expect(page).to_not have_content(block.body)
+      expect(page).not_to have_content("#{block.name} (#{block.locale})")
+      expect(page).not_to have_content(block.body)
     end
 
     scenario "From edit page" do
@@ -100,8 +100,8 @@ feature "Admin custom content blocks" do
 
       click_button "Delete block"
 
-      expect(page).to_not have_content("#{block.name} (#{block.locale})")
-      expect(page).to_not have_content(block.body)
+      expect(page).not_to have_content("#{block.name} (#{block.locale})")
+      expect(page).not_to have_content(block.body)
     end
   end
 end

spec/features/admin/site_customization/images_spec.rb

@@ -57,6 +57,6 @@ feature "Admin custom images" do
       click_link "Delete"
     end
 
-    expect(page).to_not have_css("img[src*='social_media_icon.png']")
+    expect(page).not_to have_css("img[src*='social_media_icon.png']")
   end
 end

spec/features/admin/site_customization/pages_spec.rb

@@ -22,7 +22,7 @@ feature "Admin custom pages" do
         click_link "Custom Pages"
       end
 
-      expect(page).to_not have_content "An example custom page"
+      expect(page).not_to have_content "An example custom page"
 
       click_link "Create new page"
 
@@ -65,6 +65,6 @@ feature "Admin custom pages" do
 
     click_button "Delete page"
 
-    expect(page).to_not have_content("An example custom page")
+    expect(page).not_to have_content("An example custom page")
   end
 end