[MM-46101] Move allowed protocols to build config

[devinbinnie]

Summary

The use of the electron-builder to store our default allowed protocols was causing the install to think that we should be registering Mattermost as a potential default for opening these protocols.

This PR moves the defaults to the build config, so that the only one registered for our app is mattermost, and the others will be stored elsewhere.

Ticket Link

https://mattermost.atlassian.net/browse/MM-46101

Fixed an issue where an OS might register Mattermost as the default Web Browser/Mail app