Revert "Disable chunked uploads for the 1.21 release."

This reverts commit b2aa1c9fa10cf3a01111cc5da90bbf368c71a889

(Reverted for bad RELEASE-NOTES and that this hasn't been done in core, yet.)

Change-Id: I582ba66eb89f70dbff796e14f3046fe644a26038
Merge "Revert "Disable chunked uploads for the 1.21 release."" into REL1_21