Add `libatomic1` to Ubuntu Dependencies

[Cryptoc1]

Summary

libatomic1 is a dependency that is explicitly installed in the sdk docker image, but is not specified as a dependency in the documentation, leading to unexpected behavior for users who perform manual/scripted installation of sdks.

Fixes: Sdk#51677

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docs/core/install/linux-ubuntu-install.md	Install .NET SDK or .NET Runtime on Ubuntu