Updated heartwood to version 1.6.1 and changed npmDepsHash to the value expected by nix.

Updated versions used by tests

Updated heartwood and radicle-httpd versions used by tests.

update-flake script now uses canonical release tag

Made flake only build check deps if check is run

Previously heartwood and radicle-httpd where always build when building radicle-explorer, because the checkPhase string is always interpolated.

Thank you for putting in effort to update this. I dropped the ball in reviewing it, sorry about that. Reviewing it now: https://radicle.zulipchat.com/#narrow/channel/369278-Explorer/topic/ddaa339.3A.20Updated.20heartwood.20release.20and.20npm.20deps.20in.20flake/with/590633673.

Ok, from the looks of it, most of the things proposed have been already taken care of.