Bump django from 4.2.20 to 4.2.21 in /examples/stacks/django #7027

Job	Run time
Spell Check with Typos	6s
build-devbox (ubuntu-latest)	29s
build-devbox (macos-13)	1m 29s
Test Flake Build	1m 35s
golangci-lint (ubuntu-latest)	2m 35s
golangci-lint (macos-13)	8m 21s
auto-nix-install (macos-13, false)	4m 53s
auto-nix-install (ubuntu-latest, false)	1m 43s
auto-nix-install (ubuntu-latest, true)	1m 39s
auto-nix-install (macos-13, true)	4m 48s
test (not-main, ubuntu-latest, project-tests-off, 2.20.1)	9m 59s
test (not-main, ubuntu-latest, project-tests-only, 2.20.1)	10m 45s
test (not-main, ubuntu-latest, project-tests-off, 2.12.0)	10m 35s
test (not-main, ubuntu-latest, project-tests-only, 2.12.0)	11m 31s
test (not-main, ubuntu-latest, project-tests-off, 2.19.2)	10m 5s
test-nix-versions (macos-13, 2.15.1)	5m 26s
test-nix-versions (ubuntu-latest, 2.16.1)	2m 6s
test-nix-versions (ubuntu-latest, 2.17.0)	1m 40s
test-nix-versions (macos-13, 2.16.1)	6m 10s
test-nix-versions (macos-13, 2.24.7)	3m 15s
test-nix-versions (ubuntu-latest, 2.18.0)	1m 37s
test-nix-versions (ubuntu-latest, 2.19.2)	1m 41s
test-nix-versions (ubuntu-latest, 2.24.7)	1m 33s
test-nix-versions (ubuntu-latest, 2.15.1)	2m 12s
test-nix-versions (macos-13, 2.19.2)	4m 14s
test-nix-versions (macos-13, 2.18.0)	4m 55s
test-nix-versions (macos-13, 2.17.0)	4m 6s
test (not-main, ubuntu-latest, project-tests-only, 2.19.2)	11m 8s
	2h 10m 36s

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