Do not include line numbers when copying code examples

[vhyijk]

Unexpected behavior

1. Enable the "Show line numbers on code examples" option:

   

2. Copy the code by clicking "copy code to clipboard" in the upper right corner of a code example:

   

3. Paste the code somewhere, and you'll see redundant line numbers in the code:

   

Expected behavior

Regardless of whether the "Show line numbers on code examples" option is enabled, do not include line numbers when copying code examples!

[syphar]

That's related to rustdoc, not docs.rs

@GuillaumeGomez

[GuillaumeGomez]

Seems like I missed this case when I migrated to the new line numbers DOM. Gonna fix it in the next days.