Revert "workflows/eval.misc: run tasks in parallel"

This reverts commit 3d9cb9f355.

In 3d9cb9f355 (#436171), the two check
commands were combined in the same step, and backgrounded, `wait`ing on
their completion.

`help wait` states the following:

> If ID is not given, waits for all currently active child processes,
> and the return status is zero.

The result was that this check's misc check results were accidentally
thrown away. Oops.

.github/workflows/eval.yml

@@ -453,10 +453,9 @@ jobs:
       - name: Install Nix
         uses: cachix/install-nix-action@4e002c8ec80594ecd40e759629461e26c8abed15 # v31
 
-      - name: Run misc eval tasks in parallel
+      - name: Ensure flake outputs on all systems still evaluate
+        run: nix flake check --all-systems --no-build './nixpkgs/untrusted?shallow=1'
+
+      - name: Query nixpkgs with aliases enabled to check for basic syntax errors
         run: |
-          # Ensure flake outputs on all systems still evaluate
-          nix flake check --all-systems --no-build './nixpkgs/untrusted?shallow=1' &
-          # Query nixpkgs with aliases enabled to check for basic syntax errors
-          nix-env -I ./nixpkgs/untrusted -f ./nixpkgs/untrusted -qa '*' --option restrict-eval true --option allow-import-from-derivation false >/dev/null &
-          wait
+          time nix-env -I ./nixpkgs/untrusted -f ./nixpkgs/untrusted -qa '*' --option restrict-eval true --option allow-import-from-derivation false >/dev/null