(core) README: proofread the French

Summary: Change "bien" to "beaucoup" and add a space before the exclamation mark as is usually done in French.

Test Plan: None.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D4291

README.md

@@ -202,7 +202,7 @@ and Google/Microsoft sign-ins via [Dex](https://dexidp.io/).
 
 We use [Weblate](https://hosted.weblate.org/engage/grist/) to manage translations.
 Thanks to everyone who is pitching in. Thanks especially to the ANCT developers who
-did the hard work of making a good chunk of the application localizable. Merci bien!
+did the hard work of making a good chunk of the application localizable. Merci beaucoup !
 
 <a href="https://hosted.weblate.org/engage/grist/">
 <img src="https://hosted.weblate.org/widgets/grist/-/open-graph.png" alt="Translation status" width=480 />