Revert "make-tarball.nix: Restore the 'commit' field in packages.json"

This reverts commit 5e8545e723.

It breaks eval:

attribute 'rev' missing, at /var/lib/ofborg/checkout/repo/38dca4e3aa6bca43ea96d2fcc04e8229/mr-est/eval-0-gleber.ewr1.nix.ci/pkgs/top-level/make-tarball.nix:106:39

doc/doc-support/lib-function-locations.nix

@@ -1,6 +1,6 @@
 { pkgs ? (import ./.. { }), nixpkgs ? { }}:
 let
-  revision = pkgs.lib.trivial.revisionWithDefault (nixpkgs.rev or "master");
+  revision = pkgs.lib.trivial.revisionWithDefault (nixpkgs.revision or "master");
 
   libDefPos = set:
     builtins.map

pkgs/top-level/make-tarball.nix

@@ -103,7 +103,7 @@ releaseTools.sourceTarball {
 
     header "generating packages.json"
     mkdir -p $out/nix-support
-    echo -n '{"version":2,"commit":"${nixpkgs.rev}","packages":' > tmp
+    echo -n '{"version":2,"packages":' > tmp
     nix-env -f . -I nixpkgs=${src} -qa --json --arg config 'import ${./packages-config.nix}' "''${opts[@]}" >> tmp
     echo -n '}' >> tmp
     packages=$out/packages.json.br

pkgs/top-level/release.nix

@@ -8,7 +8,7 @@
 
    $ nix-build pkgs/top-level/release.nix -A coreutils.x86_64-linux
 */
-{ nixpkgs ? { outPath = (import ../../lib).cleanSource ../..; revCount = 1234; shortRev = "abcdef"; rev = "0000000000000000000000000000000000000000"; }
+{ nixpkgs ? { outPath = (import ../../lib).cleanSource ../..; revCount = 1234; shortRev = "abcdef"; revision = "0000000000000000000000000000000000000000"; }
 , officialRelease ? false
   # The platforms for which we build Nixpkgs.
 , supportedSystems ? [ "x86_64-linux" "x86_64-darwin" "aarch64-linux" ]