Update maintaining-balance-for-open-source-maintainers.md

[kpotia]

I have the french Translation of the article https://opensource.guide/fr/maintaining-balance-for-open-source-maintainers/ in order to have a full french opensource.guide

• [ x] Have you followed the contributing guidelines?
• [ x] Have you explained what your changes do, and why they add value to the Guides?

Please note: we will close your PR without comment if you do not check the boxes above and provide ALL requested information.

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