Update node-14 still referenced in Dockerfile to 16

[jonespm]

Also update Dockerfile.openshift

This looks like was missed as part of #1312

my-learning-analytics/dockerfiles/Dockerfile

Line 24 in 458a13a

FROM node:14-slim AS node-prod-deps

[jonespm]

This might have been why some of the irregularities were noticed on that PR while we were testing this. It looks like it builds prod deps separate from the webpack.

I'd like to clean up this build and have it all as one phase or maybe 2 like Canvas App Explorer but haven't gotten around to doing that.

[jonespm]

Verified from the build logs that this builds and node:16 is now the only one referenced.