Remove link to gitter (#2584)

We do not plan to use gitter any more.

Author: jugmac00

.github/ISSUE_TEMPLATE/config.yml

@@ -1,9 +1,6 @@
 # Ref: https://help.github.com/en/github/building-a-strong-community/configuring-issue-templates-for-your-repository#configuring-the-template-chooser
 blank_issues_enabled: true # default
 contact_links:
-  - name: "💬 tox-dev/Lobby @ Gitter"
-    url: https://gitter.im/tox-dev/Lobby
-    about: Chat with devs
   - name: 🤷💻🤦 Discourse
     url: https://discuss.python.org/c/packaging
     about: |