doc(AlgebraicGeometry/RationalMap): fix module docstring (leanprover-community#39295)

`RationalMap.toPartialMap` only needs reduced, not integral.

Author: justus-springer

Mathlib/AlgebraicGeometry/RationalMap.lean

@@ -24,7 +24,7 @@ public import Mathlib.AlgebraicGeometry.Morphisms.Separated
   Given `S`-schemes `X` and `Y` such that `Y` is locally of finite type and `X` is integral,
   `S`-morphisms `Spec K(X) ⟶ Y` correspond bijectively to `S`-rational maps from `X` to `Y`.
 * `AlgebraicGeometry.Scheme.RationalMap.toPartialMap`:
-  If `X` is integral and `Y` is separated, then any `f : X ⤏ Y` can be realized as a partial
+  If `X` is reduced and `Y` is separated, then any `f : X ⤏ Y` can be realized as a partial
   map on `f.domain`, the domain of definition of `f`.
 -/