nix: Update nix packages to 25.05 — heartwood

Unfortunately, I ran into an issue with cargo-semverchecks where it could no longer recognise some metadata that cargo outputs due to a future version being unrecognised.

Updating our packages gave me a newer version of the binary and allowed me to run the checks again.

     },
     "nixpkgs-stable": {
       "locked": {
         "lastModified": 1740142985,
         "narHash": "sha256-fCPt2PVnQgiHXGlTRmU5/gFdG/+JT3ycpt+GxY1Vp+s=",
         "lastModified": 1754919767,
         "narHash": "sha256-bc9tjR2ymbmbtYlnOcksjI7tQtDDEEJFGm41t0msXsg=",
         "owner": "NixOS",
         "repo": "nixpkgs",
         "rev": "1d1ce35bb6052a23f5692cd89b7cc49acdcb8d0e",
         "rev": "8c0c41355297485b39d6f6a6d722c8cdfe0257df",
         "type": "github"
       },
       "original": {
         "owner": "NixOS",
         "ref": "release-24.11",
         "ref": "release-25.05",
         "repo": "nixpkgs",
         "type": "github"
       }
     },
     "nixpkgs-unstable": {
       "locked": {
         "lastModified": 1740142985,
         "narHash": "sha256-fCPt2PVnQgiHXGlTRmU5/gFdG/+JT3ycpt+GxY1Vp+s=",
         "lastModified": 1754919767,
         "narHash": "sha256-bc9tjR2ymbmbtYlnOcksjI7tQtDDEEJFGm41t0msXsg=",
         "owner": "NixOS",
         "repo": "nixpkgs",
         "rev": "1d1ce35bb6052a23f5692cd89b7cc49acdcb8d0e",
         "rev": "8c0c41355297485b39d6f6a6d722c8cdfe0257df",
         "type": "github"
       },
       "original": {
         "owner": "NixOS",
         "ref": "release-24.11",
         "ref": "release-25.05",
         "repo": "nixpkgs",
         "type": "github"
       }

   description = "Radicle";
   inputs = {
     nixpkgs-unstable.url = "github:NixOS/nixpkgs/release-24.11";
     nixpkgs-stable.url = "github:NixOS/nixpkgs/release-24.11";
     nixpkgs-unstable.url = "github:NixOS/nixpkgs/release-25.05";
     nixpkgs-stable.url = "github:NixOS/nixpkgs/release-25.05";
     nixpkgs.follows = "nixpkgs-stable";
     crane.url = "github:ipetkov/crane";