Fix "Example descriptions" section in style-guide

[Managor]

In the example descriptions there are various inconsistencies. It advices not to use the command name in the description while using it in the preferred examples.
The section also contains information that should be in the heading section. This section is for the descriptions of the example commands.
https://github.com/tldr-pages/tldr/blob/main/contributing-guides/style-guide.md#example-descriptions

The heading sections should also give instructions when the page needs clarification of what the brand name of a command is like in https://github.com/tldr-pages/tldr/pull/15873/files and https://github.com/tldr-pages/tldr/pull/15888/files