replace "dep" with "go mod"

A simple "go mod init && go mod tidy && go mod vendor" was enough and
mostly seems to have picked the same revisions of the dependencies as
before. Notable exceptions are klog and gogo/protobuf.

vendor/sigs.k8s.io/yaml/RELEASE.md

@@ -0,0 +1,9 @@
+# Release Process
+
+The `yaml` Project is released on an as-needed basis. The process is as follows:
+
+1. An issue is proposing a new release with a changelog since the last release
+1. All [OWNERS](OWNERS) must LGTM this release
+1. An OWNER runs `git tag -s $VERSION` and inserts the changelog and pushes the tag with `git push $VERSION`
+1. The release issue is closed
+1. An announcement email is sent to `kubernetes-dev@googlegroups.com` with the subject `[ANNOUNCE] kubernetes-template-project $VERSION is released`