feat(google-tag-manager): warn instead of throw err

[Itrulia]

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• [x] I have added tests that prove my fix is effective or that my feature works.
• [x] I have added all necessary documentation (if appropriate)

What was done

Replaced throw new Error with a console.warn like the other packages have