Update install-nix.bash

repo2docker/buildpacks/nix/install-nix.bash

@@ -2,11 +2,11 @@
 # This downloads and installs a pinned version of nix
 set -ex
 
-NIX_VERSION="2.3.9"
+NIX_VERSION="2.13.2"
 if [ "$NIX_ARCH" = "aarch64" ]; then
-  NIX_SHA256="733a26911193fdd44d5d68342075af5924d8c0701aae877e51a38d74ee9f4ff8"
+  NIX_SHA256="4ae275a46a2441d3459ae389a90ce6e8f7eff12c2a084b2d003ba6f8d0899603"
 else
-  NIX_SHA256="49763fd7fa06bcb712ced2f3f11afd275e3a4d7bc5ff0d6fd1d50a4c3ce7bbf4"
+  NIX_SHA256="beaec0f28899c22f33adbe30e4ecfceef87b797278c5210ee693e22e9719dfb4"
 fi
 
 # Do all our operations in /tmp, since we can't rely on current directory being writeable yet.