Bring in the Debian Node LTS version v16.15.0;

I took the instructions from the GitHub issue which I updated to point
to the exact comment which shows how to pin the Node version to a
specific number. But since this issue is still being updated, as 27 days
ago at the time this was written, I figured I'd leave a link to the
comment which could give us issues updated to this version of Node LTS.

Comment talking about a dependency on python2:
nodesource/distributions#33 (comment)

milmove-app/Dockerfile

@@ -55,11 +55,11 @@ ARG CACHE_APT
 RUN set -ex && cd ~ \
   && : Remove existing node \
   && rm -rf /usr/local/bin/node /usr/local/bin/nodejs \
-  && : Add Node 14.x \
+  && : Add Node 16.15.0 \
   # This is so we can pin to specific Node versions
-  # See https://github.com/nodesource/distributions/issues/33
-  # See https://deb.nodesource.com/node_14.x/pool/main/n/nodejs/ for list of packages
-  && curl -o nodejs.deb https://deb.nodesource.com/node_14.x/pool/main/n/nodejs/nodejs_14.18.1-1nodesource1_amd64.deb \
+  # See https://github.com/nodesource/distributions/issues/33#issuecomment-337767815
+  # See https://deb.nodesource.com/node_16.x/pool/main/n/nodejs/ for list of packages
+  && curl -o nodejs.deb https://deb.nodesource.com/node_16.x/pool/main/n/nodejs/nodejs_16.15.0-deb-1nodesource1_arm64.deb \
   && dpkg -i ./nodejs.deb \
   && rm nodejs.deb \
   && : Add Yarn \