Add the French translation of the news about the regression in Ruby 2.1.1

Hi,

Here is a French translation of the news about the regression of ```Hash#reject```.

I can't test the render of the news because each times I'm start the server, I get an error:

```
➜  Ruby-lang git:(master) ✗ jekyll serve
Configuration file: /Users/GRoguelon/Sites/Ruby-lang/_config.yml
            Source: /Users/GRoguelon/Sites/Ruby-lang
       Destination: /Users/GRoguelon/Sites/Ruby-lang/_site
      Generating... error: no implicit conversion of nil into String. Use --trace to view backtrace
```

I use Ruby 2.1.0 and the server had already run.

Thanks.