You can proceed in the following manner:
1. Drop a ContentBlock on your page
2. In its HTML paste:
<!-- Google Tag Manager -->
4. Select the script to be included "Where the widget is placed"
This should deliver the same HTML output as desired by Google.
Option 2 would be to paste the desired HTML in a masterpage and use this masterpage as base for this page's template.
I hope you find the above information useful.
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