Fix typo and clarify French default note 3_synchronising_your_notes.md

[narFnarF]

The French default note readme/_i18n/fr_FR/welcome/3_synchronising_your_notes.md had some typos and small errors.

Here's what I changed:

• Replace a non-breaking space in the Nextcloud title, so that markdown correctly recognize it as a title.
• Remove an extra space in the URL path

[github-actions]

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Thank you for your submission, we really appreciate it. Like many open-source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution. You can sign the CLA by just posting a Pull Request Comment same as the below format.

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I have read the CLA Document and I hereby sign the CLA

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2 out of 3 committers have signed the CLA.
✅ (narFnarF)[https://github.com/narFnarF]
✅ (laurent22)[https://github.com/laurent22]
❌ @narf
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[narFnarF]

I have read the CLA Document and I hereby sign the CLA

[narFnarF]

recheck

[personalizedrefrigerator]

Thank you for working on this @narFnarF !

The CLA Assistant workflow seems to be having trouble with this commit: e2e1ef2 (marked as authored by https://github.com/narf).

[narFnarF]

I don't know how to solve this. I made the commit with the name and noreply email that I use on Codeberg. I can't add that noreply adress in Github.

Github is so picky and complicated. I just wanted to fix a typo.... 😔