Merge pull request #7026 from zalando-incubator/skipper/update-version-v0.20.15

skipper: update version to v0.20.15

Author: szuecs

cluster/manifests/skipper/deployment.yaml

@@ -1,5 +1,5 @@
 {{ $internal_version := "v0.20.5-813" }}
-{{ $canary_internal_version := "v0.20.14-823" }}
+{{ $canary_internal_version := "v0.20.15-824" }}
 
 {{/* Optional canary arguments separated by "[cf724afc]" to allow whitespaces, e.g. "-foo=has a whitespace[cf724afc]-baz=qux" */}}
 {{ $canary_args := "" }}