Update some kep.yaml files to conform to new validation

Author: wojtek-t

keps/sig-network/1453-ingress-api/kep.yaml

@@ -30,7 +30,6 @@ latest-milestone: "v1.19"
 
 # The milestone at which this feature was, or is targeted to be, at each stage.
 milestone:
-  alpha: "pre-1.0"
   beta: "v1.1"
   stable: "v1.19"
 

keps/sig-node/1898-hardened-exec/kep.yaml

@@ -31,8 +31,6 @@ latest-milestone: "v1.20"
 # The milestone at which this feature was, or is targeted to be, at each stage.
 milestone:
   alpha: "v1.20"
-  beta: TBD
-  stable: TBD
 
 # The following PRR answers are required at alpha release
 # List the feature gate name and the components for which it must be enabled

keps/sig-node/2000-graceful-node-shutdown/kep.yaml

@@ -18,8 +18,6 @@ latest-milestone: "v1.20"
 # The milestone at which this feature was, or is targeted to be, at each stage.
 milestone:
   alpha: "v1.20"
-  beta: "x.y"
-  stable: "x.y"
 
 # The following PRR answers are required at alpha release
 # List the feature gate name and the components for which it must be enabled

keps/sig-node/2040-kubelet-cri/kep.yaml

@@ -27,7 +27,6 @@ latest-milestone: "v1.20"
 milestone:
   alpha: "v1.5"
   beta: "v1.20"
-  stable: TBD
 
 # The following PRR answers are required at beta release
 metrics:

keps/sig-storage/1698-generic-ephemeral-volumes/kep.yaml

@@ -15,8 +15,6 @@ stage: alpha
 latest-milestone: "v1.19"
 milestone:
   alpha: "v1.19"
-  beta: ""
-  stable: ""
 feature-gates:
   - name: GenericEphemeralVolumes
     components: