bats: fixes installation

The build was failing with:

/...-stdenv/setup: ./install.sh: /usr/bin/env: bad interpreter: No such file
or directory

See https://hydra.nixos.org/build/32353411/log

pkgs/development/interpreters/bats/default.nix

···
     sha256 = "05xpvfm0xky1532i3hd2l3wznxzh99bv2hxgykwdpxh18h6jr6jm";
   };
 
+  patchPhase = "patchShebangs ./install.sh";
+
   installPhase = "./install.sh $out";
 
   meta = with stdenv.lib; {