Saving multiple google tag Id isn't working

Problem/Motivation

Adding multiple google tag ID on the setting form is saving only first ID.

Steps to reproduce

1. Visit path: admin/config/services/google-tag
2. Enter google tag ID and click on add another Id button.
3. Enter 3-4 google tag ID and click on SAVE button

Remaining tasks

All Google tag ID's should be saved properly in the settings and configuration form at first instance.