Replace Channel Name for Team in Email Notifications (#7839)

* allow option to set channel name in email notification subject

* Added TeamName to title when UseChannelInEmailNotifications=true

config/default.json

@@ -143,6 +143,7 @@
         "EnableSignInWithEmail": true,
         "EnableSignInWithUsername": true,
         "SendEmailNotifications": true,
+        "UseChannelInEmailNotifications": false,
         "RequireEmailVerification": false,
         "FeedbackName": "",
         "FeedbackEmail": "test@example.com",