Removing use of kubectl --show-all in docs
Removing use of kubectl --show-all in docs

--show-all has been deprecated in kubernetes v1.15
Resolves #1814

Signed-off-by: Hays Clark <03c781cd4628763af2a703b528920fc471c58666@gmail.com>

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