chore(deps): update debian docker tag to v11 (#334)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

variables.sh

@@ -6,7 +6,7 @@ NAMESPACE=${NAMESPACE:-namely}
 CONTAINER=${DOCKER_REPO}${NAMESPACE}
 LATEST=${1:false}
 
-DEBIAN_VERSION=${DEBIAN_VERSION:-buster}
+DEBIAN_VERSION=${DEBIAN_VERSION:-bullseye}
 GO_VERSION=${GO_VERSION:-1.17}
 GRPC_VERSION=${GRPC_VERSION:-1.48}
 GRPC_JAVA_VERSION=${GRPC_JAVA_VERSION:-1.48}