Changes security template to use releases channel

Mayra Cabrerarequested to merge
notify-releases-instead-of-development into master

What does this MR do?

When performing a security patch, auto-deploy processes are temporarily stopped until the security release is out. We manually post a modification on #development to notify about this, but this Slack channel is very polluted and the message can get easily lost. #releases channel on slack seems more appropriate.

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