Update Dockerfile syntax version to 1.16

https://docs.docker.com/build/buildkit/dockerfile-release-notes/

Author: pdabelf5

build/Dockerfile

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.6
+# syntax=docker/dockerfile:1.16
 ARG BUILD_OS=debian
 ARG NGINX_PLUS_VERSION=R34
 ARG DOWNLOAD_TAG=edge

build/dependencies/Dockerfile.ubi8

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.8
+# syntax=docker/dockerfile:1.16
 FROM redhat/ubi8@sha256:244e9858f9d8a2792a3dceb850b4fa8fdbd67babebfde42587bfa919d5d1ecef AS rpm-build
 RUN mkdir -p /rpms/ \
     && dnf install rpm-build gcc make cmake -y \

build/dependencies/Dockerfile.ubi9

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.8
+# syntax=docker/dockerfile:1.16
 FROM redhat/ubi9:9.5@sha256:d07a5e080b8a9b3624d3c9cfbfada9a6baacd8e6d4065118f0e80c71ad518044 AS rpm-build
 RUN mkdir -p /rpms/ \
     && dnf install rpm-build gcc make cmake -y \

tests/Dockerfile

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.11
+# syntax=docker/dockerfile:1.16
 # this is here so we can grab the latest version of kind and have dependabot keep it up to date
 FROM kindest/node:v1.33.1@sha256:050072256b9a903bd914c0b2866828150cb229cea0efe5892e2b644d5dd3b34f