ci: Format nixfmt command prominently (NixOS#373939)

Author: infinisil

.github/workflows/check-nix-format.yml

@@ -91,8 +91,10 @@ jobs:
           if (( "${#unformattedFiles[@]}" > 0 )); then
             echo "Some new/changed Nix files are not properly formatted"
             echo "Please format them using the Nixpkgs-specific \`nixfmt\` by going to the Nixpkgs root directory, running \`nix-shell\`, then:"
+            echo
             echo "nixfmt ${unformattedFiles[*]@Q}"
-            echo "Make sure your branch is up to date with master, rebase if not."
+            echo
+            echo "Make sure your branch is up to date with master; rebase if not."
             echo "If you're having trouble, please ping @NixOS/nix-formatting"
             exit 1
           fi