Merge pull request kubernetes#4498 from liggitt/4193-beta

KEP-4193: Update kep to beta

Author: k8s-ci-robot

keps/sig-auth/4193-bound-service-account-token-improvements/kep.yaml

@@ -18,7 +18,7 @@ see-also: []
 replaces: []
 
 # The target maturity stage in the current dev cycle for this KEP.
-stage: alpha
+stage: beta
 
 # The most recent milestone for which work toward delivery of this KEP has been
 # done. This can be the current (upcoming) milestone, if it is being actively