chore: remove fish

overlays/fish/default.nix

@@ -1,12 +0,0 @@
-# Workaround for aarch64-darwin codesigning bug (nixpkgs#208951 / #507531):
-# fish binaries from the binary cache occasionally have invalid ad-hoc
-# signatures on Apple Silicon. Forcing a local rebuild ensures codesigning
-# is applied on this machine with a valid signature.
-{ inputs, ... }:
-final: prev: {
-  fish = prev.fish.overrideAttrs (_old: {
-    # Bust the cache key so fish is always built locally rather than
-    # substituted from the binary cache where the signature may be stale.
-    NIX_FORCE_LOCAL_REBUILD = "darwin-codesign-fix";
-  });
-}