postgresql: refactor to move locale-binary-path.patch into patches/

Seems to have been put in the wrong place.

pkgs/servers/sql/postgresql/default.nix

···
       ./patches/findstring.patch
 
       (substituteAll {
-        src = ./locale-binary-path.patch;
+        src = ./patches/locale-binary-path.patch;
         locale = "${if stdenv.isDarwin then darwin.adv_cmds else lib.getBin stdenv.cc.libc}/bin/locale";
       })