Github: disable dependabot

[yurtpage]

I wanted to check open PRs but the page is polluted with dependency updates from the dependabot.
Please disable it: it would be better to update deps manually before a beta release.

Same for the main repo where it's 11 PRs from the bot https://github.com/conversejs/converse.js/issues?q=is%3Apr%20is%3Aopen%20author%3Aapp%2Fdependabot

[kicken]

You can filter the results to exclude the dependabot PRs using -author:app/dependabot