Update soroban-dev image to use 20.0.0 versions#529

Merged

sreuland merged 3 commits intostellar:masterfrom sreuland:release-20.0.0

Dec 7, 2023

+11-12

Commits on Dec 7, 2023

stellar#527 : updated testing and soroban-dev images to use 20.0.0 versions
sreuland
committed
stellar#527 : revert testing image back to prior soroban release
sreuland
committed
stellar#527 : revert build-testing target back to prior soroban version
sreuland
committed