Remove CircleCI configuration - now using GitHub Actions

[madpah]

To align with latest Community Standards.

[github-actions]

Hi!

First of all, thank you for opening your first issue. Elementary, we appreciate all feedback that helps us continue improving this plugin.

As this is a community project we can't commit to official due dates for reviews and developing, but we're definitely committed to delivering services, integrations and plugins of top quality.

So please be patient, we will review your issue and get back to you as soon as we can!

Regards,
Sherlock Trunks 🐘