Install PolicyKit rule with 0644 permissions
The PolicyKit rule is installed with 0640 permissions, but polkitd
runs under an unprivileged user. As a result, the action is not parsed and running pkexec brillo
falls back to the generic org.freedesktop.policykit.exec
action. Installing with 0644 permissions allows polkitd
to parse the action and make pkexec brillo
work as expected.