unpin golink flake input when nixpkgs reaches go 1.26.6

[stackptr]

golink's main branch bumped its go.mod minimum to go 1.26.6, but nixpkgs currently ships 1.26.5. To unblock spore builds, the golink input was pinned to 52e1fd1 (the last commit requiring only 1.26.5) in #535.

When nixpkgs-unstable bumps to go 1.26.6, unpin golink in flake.nix:

golink = {
  url = "github:tailscale/golink";  # remove the commit pin
  inputs.nixpkgs.follows = "nixpkgs";
  inputs.systems.follows = "systems";
};

Then run nix flake update --commit-lock-file to pick up the latest golink.