Revert "Add gtm_anon_id to dataLayer"

This reverts commit a8d1b0b.

Author: BenMillar-MOJ

app/templates/components/gtm.html

@@ -14,8 +14,4 @@
   gtag('js', new Date());
 
   gtag('config', '{{ gtm_measurement_id }}');
-
-  {% if gtm_anon_id %}
-  window.dataLayer.push({ user_id: "{{ gtm_anon_id }}" });
-  {% endif %}
 </script>