Switch back to upstream devenv flake

changelog.d/15533.misc

@@ -0,0 +1 @@
+Install the `xmlsec` package and switch back to the upstream [cachix/devenv](https://github.com/cachix/devenv) repo in the nix development environment.

flake.nix

@@ -50,11 +50,7 @@
     # Output a development shell for x86_64/aarch64 Linux/Darwin (MacOS).
     systems.url = "github:nix-systems/default";
     # A development environment manager built on Nix. See https://devenv.sh.
-    # This is temporarily overridden to a fork that fixes a quirk between
-    # devenv's service and python language features. This can be removed
-    # when https://github.com/cachix/devenv/pull/559 is merged upstream.
-    devenv.url = "github:anoadragon453/devenv/anoa/fix_languages_python";
-    #devenv.url = "github:cachix/devenv/main";
+    devenv.url = "github:cachix/devenv/main";
     # Rust toolchains and rust-analyzer nightly.
     fenix = {
       url = "github:nix-community/fenix";