chore(3p/sources): Bump channels & overlays

- agenix has not been updated (waiting for
  https://github.com/ryantm/agenix/pull/241).

- libgit2_1_5 can be removed (no longer used by cargo-audit).

Change-Id: I96c6a1a4175dc4f2a32b9b2e4ed71caa826a9c42
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11077
Tested-by: BuildkiteCI
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: flokli <flokli@flokli.de>

third_party/overlays/tvl.nix

@@ -122,10 +122,6 @@ depot.nix.readTree.drvTargets {
     '';
   };
 
-  # Disable tests which fail and weren't executed before the bump that
-  # introduced this problem: https://github.com/NixOS/nixpkgs/issues/288064
-  libgit2_1_5 = super.libgit2_1_5.overrideAttrs (_: { doCheck = false; });
-
   evans = super.evans.overrideAttrs (old: {
     patches = old.patches or [ ] ++ [
       # add support for unix domain sockets