 add code-block:: shell to Helmfile alternative install
 add code-block:: shell to Helmfile alternative install

Signed-off-by: Nicolas Kowenski <d659c10e27d52b00987b65e85d99bce5480adcae@garufa.ethz.ch>

jetstack-experimental/cert-manager,jetstack/cert-manager,cert-manager/cert-manager,jetstack/cert-manager,cert-manager/cert-manager,cert-manager/cert-manager,jetstack-experimental/cert-manager,jetstack/cert-manager,jetstack-experimental/cert-manager