Change README build steps to use the official ESP-IDF image (backport #300)

[mergify]

Main changes

This PR removes the README references to the deprecated Micro-ROS ESP-IDF docker image, changing the build steps to use the Espressif's official one.

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This is an automatic backport of pull request #300 done by Mergify.

[mergify]

Cherry-pick of 3fb203b has failed:

On branch mergify/bp/humble/pr-300
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Unmerged paths:
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	both modified:   README.md

no changes added to commit (use "git add" and/or "git commit -a")

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