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

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"


Open c.html.markdown around line 819 and compare the explanation with C's float formatting behavior shown in the issue. Update the wording so it describes the minimum width and two digits to the right of the decimal point, then verify the rendered snippet matches the example.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.