ci: use go 1.16 for deps-check

What does this MR do?

Use go 1.16 image when running make deps-check.

After rebasing on master I've noticed make deps-check was failing on my local machine (go 1.16.6). Upon further investigation it turned out the behaviour of go mod tidy changed since go 1.14. See failing pipeline for details.

TODO

• I added the Changelog (e.g. Changelog: feature) trailer to the commits that need to be included in the changelog
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines