[google-cloud-cpp] update to latest release (v1.21.0)#14886

Merged

BillyONeal merged 2 commits intomicrosoft:masterfrom

coryan:update-google-cloud-cpp-v1.21.0

Dec 4, 2020

Commits on Dec 2, 2020

[google-cloud-cpp] update to latest release (v1.21.0)
coryan
committed

Commits on Dec 3, 2020

Merge remote-tracking branch 'origin/master' into HEAD
BillyONeal
committed