maintainers/upload-release.pl: Delete temporary directories when we'r… #12966

Job	Run time
vm_tests	22m 22s
Check Cachix and Docker secrets present for installer tests	1s
meson_build (ubuntu-latest)	10m 52s
meson_build (macos-latest)	4m 45s
tests (ubuntu-latest)	53m 47s
tests (macos-latest)	42m 50s
flake_regressions	20m 53s
installer	47m 15s
docker_push_image	0s
installer_test (ubuntu-latest)	30s
installer_test (macos-latest)	1m 10s
	3h 24m 25s

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