Auto merge of #150395 - GuillaumeGomez:fix-copy-code-example-with-line-numbers, r=yotamofek

Fix copy code example with line numbers

Fixes rust-lang/rust#150339.

Since the line numbers are now included in the actual highlighted code, we need to filter them out when we "copy" the code.

r? `@yotamofek`

Author: bors