Updates the deploy guide to what worked with Phoenix and Liveview as …

[tapickell]

…of today

Fix for issue
#5557

The deploy guide for Heroku is not 100% accurate anymore.
I followed them the best I could but a couple things just did not work correctly.

I could not deploy to master as Heroku is using main now for Git.
Once deployed web sockets would not connect.
I added the PHX_HOST env var and that resolved it.

The PHX_HOST issue may be a deeper issue with the config recommendations for adding the host.
That part did seem to not 100% reflect the current state of a new Phoenix application for 1.7.7
The setting the env var may be a band-aid.
If anyone has more insight into that please let me know and I will make changes to this PR.

The example app I tested with: https://github.com/tapickell/url_short_link

[Gazler]

Thanks for the PR.

I think we simply want to remove this part:

https://github.com/tapickell/url_short_link/blob/main/config/prod.exs#L10

So for the guide, we can change the preparing for heroku section:

phoenix/guides/deployment/heroku.md

Line 164 in 69bcfdf

url: [scheme: "https", host: "mysterious-meadow-6277.herokuapp.com", port: 443],

To set the environment variable you have set in your PR.