ci: update gke version
The google cloud release notes indicate that we need to upgrade:
cloud.google.com/kubernetes-engine/docs/release-notes#october_02_2020_r32
@@ -1061,7 +1061,7 @@ jobs:
default: 1
gke-version:
type: string
- default: "1.16.13-gke.1"
+ default: "1.16.15-gke.500"
machine-type:
type: string
default: "n1-standard-8"
