Use @" register instead of @s

Previously `gv"sy` yanked not only into register `@s`, but also into register `@"`, while only `@s` gets restored afterwards.

To confirm this, yank some text into `@"` with `yiw`, visually select and search some other text `v$*` and paste with `p`. This will not paste the originally yanked word.

This pull request uses and restores the `@"` register instead. The above example pastes the originally yanked word as expected.