Ubuntu 20.04 buildtools containers are EOL: dotnet/dotnet-buildtools-prereqs-docker#1449

References to these images need to be upgraded to a supported version:

• efcore/eng/helix.proj

  Line 20 in 8a8e758

  <HelixTargetQueues Condition = "'$(HelixTargetQueues)' == ''">Windows.10.Amd64.Open;OSX.1200.Amd64.Open;OSX.1200.ARM64.Open;[email protected]/dotnet-buildtools/prereqs:ubuntu-20.04-helix-sqlserver-amd64</HelixTargetQueues>

• efcore/azure-pipelines.yml

  Line 233 in 8a8e758

  value: Windows.10.Amd64;OSX.13.Amd64;OSX.13.ARM64;[email protected]/dotnet-buildtools/prereqs:ubuntu-20.04-helix-sqlserver-amd64

• efcore/azure-pipelines-public.yml

  Line 154 in 8a8e758

  value: Windows.10.Amd64.Open;OSX.13.Amd64.Open;[email protected]/dotnet-buildtools/prereqs:ubuntu-20.04-helix-sqlserver-amd64

These changes also need to be backported to the servicing branches.