[c/en] Wrong explanation of "float"s formatting in C

[hatkidchan]

https://github.com/adambard/learnxinyminutes-docs/blob/fbaa905e23f26d20b37a3886dd8e07cd6edb8680/c.html.markdown#L819

This actually means "minimum 3 characters, including decimal point with 2 digits on the right of it"