[SSR] Remove `styleDedupe` signature change warning from next release

[wjhsf]

#5271 was supposed to be a fast follow to #5264 with a change to the signature. But then I got sick and it wasn't. Now the original signature is being used, so we can't just change and release. But SSR v2 is still technically experimental, and not that many people are using it, so we added a warning when using the old signature so that people know to change their usage. That's very temporary, so we should remove it as soon as they do.