The ``oca-gen-addon-readme`` entry is a multi-line YAML scalar. The
prettier hook rewrites it on every run in each target repo, producing a
recurring local diff against the deployed copy. Format the source configs
with the exact prettier versions deployed per version (2.7.1 for 16.0,
3.3.3 for 18.0) so the deployed files already match the hook output.
No functional change: YAML folds the scalar newlines into spaces either
way.
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