Remove $NIX_USER_PROFILE_DIR

This is not used anywhere.

scripts/nix-profile-daemon.sh.in

@@ -2,7 +2,6 @@
 if [ -n "${__ETC_PROFILE_NIX_SOURCED:-}" ]; then return; fi
 __ETC_PROFILE_NIX_SOURCED=1
 
-export NIX_USER_PROFILE_DIR="@localstatedir@/nix/profiles/per-user/$USER"
 export NIX_PROFILES="@localstatedir@/nix/profiles/default $HOME/.nix-profile"
 
 # Set $NIX_SSL_CERT_FILE so that Nixpkgs applications like curl work.

scripts/nix-profile.sh.in

@@ -5,7 +5,6 @@ if [ -n "$HOME" ] && [ -n "$USER" ]; then
 
     NIX_LINK=$HOME/.nix-profile
 
-    NIX_USER_PROFILE_DIR=@localstatedir@/nix/profiles/per-user/$USER
 
     # Append ~/.nix-defexpr/channels to $NIX_PATH so that <nixpkgs>
     # paths work when the user has fetched the Nixpkgs channel.
@@ -35,5 +34,5 @@ if [ -n "$HOME" ] && [ -n "$USER" ]; then
     fi
 
     export PATH="$NIX_LINK/bin:$PATH"
-    unset NIX_LINK NIX_USER_PROFILE_DIR
+    unset NIX_LINK
 fi