Vim and emacs modelines are used to specify some of the code style in the code.
However, this is misleading and poorly supported since nautilus had a mix of
code style for some time.
Also, the mode lines doesn't specify the whole code style, so we will need to
use a different tool as well to specify the whole code style.
For that, we can just use a different tool for everything.

So remove the mode lines, and in a short future we will reestyle the nautilus
code to have a single code style, and use a tool like editorconfig to specify
the whole code style.