[Snyk] Security upgrade ubuntu from 16.04 to xenial-20210416#5

Open

snyk-bot wants to merge 1 commit intomasterfrom snyk-fix-837435de9196cc5ae8bb2d2af1cddea7

+1-1

Commits on Aug 1, 2021

fix: docker/travis-build-environment-ubuntu/Dockerfile to reduce vulnerabilities
snyk-bot
committed