[Snyk] Security upgrade ubuntu from 16.04 to xenial-20210416#21

Open

snyk-bot wants to merge 1 commit intomasterfrom

snyk-fix-590ca78f00c55bcd9d8a5605641fcf4d

Commits on Aug 1, 2021

fix: doc/getting-started/getting-started.dockerfile to reduce vulnerabilities
snyk-bot
committed