Revert discarding penultimate sigma for DPM-Solver++(2M) SDE

[catboxanon]

Description

Reverts https://github.com/AUTOMATIC1111/stable-diffusion-webui/pull/10586. Doing this in preparation of https://github.com/AUTOMATIC1111/stable-diffusion-webui/pull/10634 or https://github.com/AUTOMATIC1111/stable-diffusion-webui/pull/10649 being merged.

Checklist:

• [x] I have read contributing wiki page
• [x] I have performed a self-review of my own code
• [x] My code follows the style guidelines
• [x] My code passes tests

[AUTOMATIC1111]

why revert

[catboxanon]

https://github.com/AUTOMATIC1111/stable-diffusion-webui/pull/10586#issuecomment-1556375281, also the fact that exposing scheduler and sigma controls removes the explicit need for this.

[catboxanon]

Well now that a new release was pushed with this change, we likely would need to document this as a breaking seed change if it were merged...