Update workflows implemented by the LVGL team

[minyiky]

Summary

In trying to see if the issues I was having locally were also seen in the CI pipeline I noticed that the runners seem to be deprecated for many of the actions authored by the LVGL team, I have updated to use ubuntu latest rather than a pinned version of the OS.

Testing

This will be tested as part of the PR due to the CI pipelines being triggered

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Summary by cubic

Switch GitHub Actions runners from ubuntu-20.04 to ubuntu-latest to avoid deprecated environments and keep LVGL actions supported. Applies to js-port-v9, merge-to-js, rp2_port, stm32_port, and unix_port workflows.