johngmyers: Recommend kops 1.21.0 in alpha channel

JobBuild
12051
07-27 04:37
pull-kops-bazel-build 1419879404548395008
pull-kops-bazel-test 1419879404581949440
pull-kops-e2e-kubernetes-aws 1419879404514840576
pull-kops-verify-bazel 1419879404619698176
pull-kops-verify-boilerplate 1419879404711972864
pull-kops-verify-generated 1419879404644864000
pull-kops-verify-gofmt 1419879404749721600
pull-kops-verify-gomod 1419879404682612736
pull-kops-verify-govet 1419879404779081728
pull-kops-verify-staticcheck 1419879404808441856