SSE tab limit doesn't appear to work

[ColdHeat]

We do not seem to be releasing the SSE connection with each tab. We need to release the connection if we have too many tabs because users will be unable to interact with CTFd if they have too many tabs open.

[ColdHeat]

To reproduce, simply open 6+ tabs of CTFd when using core-beta. The later tabs should not load.

[ColdHeat]

Might need to spend some time investigating this.

[ColdHeat]

It appears that this does happen under http1.1 but not under http2 because the connection limit is increased. The simple solution is to switch to http2 but fixing controller.js would be a better long term fix.