Revert "nix/libgit2: Unpatch irrelevant fix for quick delivery"

This reverts commit f7b37bf885.

That commit was a workaround to avoid rebuilding Nix and the NixOS
tests, which was a safe thing to do.
This commit targets the staging-nixos cycle, so that we can make Nix
use the normal libgit2 package again.

pkgs/tools/package-management/nix/dependencies.nix

@@ -34,12 +34,5 @@ regular@{
       # only a stripped down version is built which takes a lot less resources to build
       requiredSystemFeatures = [ ];
     };
-
-    libgit2 = pkgs.libgit2.overrideAttrs (old: {
-      # Drop the SSH buffer overflow patch to avoid rebuilding Nix
-      patches = lib.filter (p: !lib.hasSuffix "fix-ssh-custom-heap-buffer-overflow.patch" (toString p)) (
-        old.patches or [ ]
-      );
-    });
   };
 }