Switched to dev branch

[girish]

We switched pixelfed to build from the dev branch instead of the tagged releases. This seems to be recommended by their upstream docs as well - https://docs.pixelfed.org/running-pixelfed/installation/#download-source-via-git . It's unlikely any bugs found are fixed in old tagged releases, so it makes sense to switch. The last tagged releases is quite far behind dev branch.

This, of course, adds some instability. But "Pixelfed is still a work in progress. We do not recommend running an instance in production at this stage unless you know what you are doing!" is what it says on the sticker.

Thanks to @doodlemania2 for the suggestion.