Revert "[VPlan] Mark recurrence recipes as not having side-effects."

This reverts commit 02369b75.

At the moment, live-outs used *only* for the resume values in the scalar
loop are not modeled in VPlan yet. This means first-order recurrence
recipes could be removed, when a scalar epilogue is required and the
only use of a FOR is outside the loop.

Keep treating recurrence recipes as having side-effects for now, to
avoid them being removed.

Fixes #62954.