fix(CSS): too much overflow in the example output

[OnkarRuikar]

• Fixes Overflowing content overlaps the interactive editor content#27975

If we update width we won't have to update mdn/content side. With width 350px the overflow doesn't spill over the output area.

To test the change try the width in the live sample https://developer.mozilla.org/en-US/docs/Learn/CSS/Building_blocks/Overflowing_content#css_tries_to_avoid_data_loss

[haocheng6]

Would it make sense to also update the width of some other examples on that page (for example, the first example under the The overflow property section) to make them look consistent?

[sideshowbarker]

I unfortunately don’t have merge perms for this repo

[chrisdavidmills]

I unfortunately don’t have merge perms for this repo

Me neither ;-(

[rachelandrew]

I used to so just checked but don't anymore :D