Install g++-11 (for c++20) support

[sashaDoubov]

What does this PR do?

This ensures that g++11 is installed in the docker image, allowing us to leverage c++20 features.

What issue(s) does this change relate to?

Not related to an open issue.

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[sashaDoubov]

since we have bumped to ubuntu22.04, this explicit installation is not needed.