[Doc] Delete Extra TOC Text from 'Coding Standard' Page

[tianheg]

While reading the documentation, I noticed extra text at the bottom of the Table of Contents on the Coding Standard page:

The last two lines of text, 'Code Style' and 'Language features', are unnecessary and should be removed.

I couldn't locate the problem in the code as I am not familiar with it. Therefore, I created this issue to request assistance in rectifying the problem.