feat: remove github.api_token configuration option

Author: lykimq

example-config.toml

@@ -20,8 +20,7 @@ port="8000" # The port number the server is listening on.
 # Settings for GitHub
 [github]
 # If commented, these secrets are read from environment
-# variables: GITHUB_ACCESS_TOKEN and GITHUB_WEBHOOK_SECRET
-api_token="secret"
+# variables: GITHUB_WEBHOOK_SECRET
 webhook_secret="secret"
 app_id="0" # The GitHub App ID