Change uses of `innerHTML` to `textContent`

Since you never use the feature of [`innerHTML`] to embed HTML, it is safer and faster to use [`textContent`] instead.

[`innerHTML`]: https://developer.mozilla.org/en-US/docs/Web/API/Element.innerHTML
[`textContent`]: https://developer.mozilla.org/en-US/docs/Web/API/Node.textContent

You will probably have to regenerate the bookmarklet to match the source code of `ssc.user.js`, however you do that.

I did not attempt testing this change, because it would be hard to prevent my changed code from conflicting with the version of this script that the actual side loads.