update pg_cron to 1.6.4 (supabase#1208)

Author: olirice

nix/ext/pg_cron.nix

@@ -2,15 +2,15 @@
 
 stdenv.mkDerivation rec {
   pname = "pg_cron";
-  version = "1.6.2";
+  version = "1.6.4";
 
   buildInputs = [ postgresql ];
 
   src = fetchFromGitHub {
     owner  = "citusdata";
     repo   = pname;
     rev    = "v${version}";
-    hash = "sha256-/dD1gX0+RRsBFIjSV9TVk+ppPw0Jrzssl+rRZ2qAp4w=";
+    hash = "sha256-t1DpFkPiSfdoGG2NgNT7g1lkvSooZoRoUrix6cBID40=";
   };
 
   installPhase = ''