Added missing optional (software-mansion#2229)

## Description

Added missing optional to the callback in animation builder - this broke building script.

src/reanimated2/layoutReanimation/animationBuilder/LayoutAnimationBuilder.ts

@@ -19,7 +19,7 @@ export class LayoutAnimationBuilder implements ILayoutAnimationBuilder {
   overshootClampingV?: number;
   restDisplacementThresholdV?: number;
   restSpeedThresholdV?: number;
-  callbackV: (finished: boolean) => void;
+  callbackV?: (finished: boolean) => void;
 
   static duration(durationMs: number): LayoutAnimationBuilder {
     const instance = new LayoutAnimationBuilder();