overlay: include yarr (consuming nixpkgs has rustc 1.97.1)

yarr needs rustc 1.97.1. The mcp-servers flake's own nixpkgs has 1.95,
but consuming flakes (config-nixos) pin a newer nixpkgs with 1.97.1.
Since rustPkgs defaults to the consuming pkgs, yarr builds fine in the
overlay there. Remove the removeAttrs exclusion.

overlays/default.nix

@@ -15,12 +15,8 @@
 #       # Now pkgs.manim-mcp-server is available
 #     };
 #   }
-#
-# Note: yarr is excluded from the overlay because it needs rustc 1.97.1
-# from a specific nixpkgs input. Build it via nix build .#yarr on the
-# flake directly.
 final: prev:
 let
   mcpPackages = import ../packages { pkgs = final; };
 in
-builtins.removeAttrs mcpPackages [ "yarr" ]
+mcpPackages