PyPi `imgtool` package is out of date

[JordanYates]

The version of imgtool distributed through PyPi is out of date. Specifically, it does not contain the fixes contained in #1973.

[utzig]

No release was made after that PR was merged, so either wait for 2.2.0 or suggest/PR a beta release of imgtool.

[github-actions[bot]]

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