You may have received the following email:
Your org has been identified as having users or integrations still connecting to Salesforce using TLS 1.0 encryption protocol.
You are wondering if Heroku Connect is a contributing factor.
Heroku Connect is fully compatible with TLS 1.1.
The Heroku Connect API and Heroku Connect Dashboard now require TLS version 1.1 or higher and this is effective since 05 December 2017.