Don't use instace variables in component views

Just like we do every else (sometimes even on that very same file), we
use the method instead of the instance variable.

We're doing this change now because we're about to modify one of these
files (the poll question answers documents index component).

app/components/admin/site_customization/pages/edit_component.html.erb

@@ -4,7 +4,7 @@
 <%= header do %>
   <%= render Admin::ActionComponent.new(
     :destroy,
-    @page,
+    page,
     text: t("admin.site_customization.pages.index.delete"),
     confirm: true,
     class: "delete"