i18n(fr): improve the wording in upgrade-to/v3.mdx

[ArmandPhilippot]

Description (required)

Improves the wording in the French translation of upgrade-to/v3.mdx based on #11593 and #11795

• update the translation of breaking changes, upgrade, deprecated, flag
• replace le CLI with la CLI
• replace the translation of build where more appropriate
• small fixes and rewording to make the reading easier

Related issues & labels (optional)

• Suggested label: i18n

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fr/guides/upgrade-to/v3.mdx	Localization changed, will be marked as complete.
fr/guides/upgrade-to/v4.mdx	Localization changed, will be marked as complete.

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🔄️	The source for this localization has been updated since the creation of this pull request, make sure all changes in the source have been applied.