Fix package location for build flags (#1979)

Co-authored-by: David Simansky <[email protected]>

Author: knative-prow-robot

hack/build-flags.sh

@@ -16,7 +16,7 @@ function build_flags() {
   local now rev
   now="$(date -u '+%Y-%m-%d %H:%M:%S')"
   rev="$(git rev-parse --short HEAD)"
-  local pkg="knative.dev/client/pkg/kn/commands/version"
+  local pkg="knative.dev/client/pkg/commands/version"
   local version="${TAG:-}"
   # Use vYYYYMMDD-local-<hash> for the version string, if not passed.
   if [[ -z "${version}" ]]; then