Update cancel URL handling in HTTP and timer function templates

- Modify header template to use explicit `cancel_url` parameter
- Add `cancel_url` to new timer and HTTP function templates
- Remove default URL fallback in header template

templates/dashboard/timer_functions/edit.html

@@ -2,7 +2,8 @@
 
 {% block page %}
 
-{{ render_partial('dashboard/http_functions/header.html', function_id=function_id,
+{{ render_partial('dashboard/http_functions/header.html',
+function_id=function_id,
 active_tab='edit',
 show_edit_form=True,
 show_logs=True,