Improve French translation

[CoBC]

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• [x] 🧪 Added tests for changed code.
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Description of Changes

Updated French localization to use capitalize letters (typically always use in French) and fix january abreviation

[anishnya]

@jadchaar @krisfremen @systemcatch, do you mind taking a look here? I don't believe we've enforced a standard on capitalization?

[krisfremen]

True, we've never enforced capitalization, but we can start doing that, maybe defer to what CLDR has for capitalisation?

[krisfremen]

We'll defer to the CLDR for capitalization, where currently it is lowercase.