Upgrade Debian base images from 10.7 to 10.8.

Signed-off-by: Matt Moyer <moyerm@vmware.com>

hack/lib/tilt/Tiltfile

@@ -152,7 +152,7 @@ k8s_yaml(local([
     '--data-value namespace=concierge ' +
     '--data-value image_repo=image/concierge ' +
     '--data-value image_tag=tilt-dev ' +
-    '--data-value kube_cert_agent_image=debian:10.7-slim ' +
+    '--data-value kube_cert_agent_image=debian:10.8-slim ' +
     '--data-value discovery_url=$(TERM=dumb kubectl cluster-info | awk \'/master|control plane/ {print $NF}\') ' +
     '--data-value log_level=debug ' +
     '--data-value-yaml replicas=1 ' +

hack/lib/tilt/concierge.Dockerfile

@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 # Use a runtime image based on Debian slim
-FROM debian:10.7-slim
+FROM debian:10.8-slim
 
 # Copy the binary which was built outside the container.
 COPY build/pinniped-concierge /usr/local/bin/pinniped-concierge

hack/lib/tilt/local-user-authenticator.Dockerfile

@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 # Use a runtime image based on Debian slim
-FROM debian:10.7-slim
+FROM debian:10.8-slim
 
 # Copy the binary which was built outside the container.
 COPY build/local-user-authenticator /usr/local/bin/local-user-authenticator

hack/lib/tilt/supervisor.Dockerfile

@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 # Use a runtime image based on Debian slim
-FROM debian:10.7-slim
+FROM debian:10.8-slim
 
 RUN apt-get update && apt-get install -y ca-certificates && rm -rf /var/lib/apt/lists/*