chore(rootfs/Dockerfile): update golangci-lint to v1.31.0 (#251)

See https://github.com/golangci/golangci-lint/releases/tag/v1.31.0

Author: mboersma

rootfs/Dockerfile

@@ -11,7 +11,7 @@ ENV AZCLI_VERSION=2.12.1 \
     HELM_VERSION=v2.16.9 \
     KUBECTL_VERSION=v1.16.3 \
     ETCDCTL_VERSION=v3.1.8 \
-    GOLANGCI_LINT_VERSION=v1.30.0 \
+    GOLANGCI_LINT_VERSION=v1.31.0 \
     PROTOBUF_VERSION=3.7.0 \
     SHELLCHECK_VERSION=v0.7.1 \
     SHFMT_VERSION=3.1.2 \