Our direnv integration was making zed refuse to auto-update when you had
the zed repo open with the devshell active. This was happening even when
you used a non-nix build of zed, which actually should be able to
auto-update.
I'm a bit unsure of why we check for the `ZED_UPDATE_EXPLANATION` env
var [both at build time _and_ at
runtime](2828dcb67b/crates/auto_update/src/auto_update.rs (L149)),
but I can see an argument for why people might want that so I'll just do
the less intrusive change for now and leave the var out of the devshell.
Release Notes:
- N/A
22d905dc03