fix: refine Fn type definition

Signed-off-by: Jérôme Benoit <[email protected]>

src/types.ts

@@ -4,7 +4,7 @@ import type Task from '../src/task';
  * the task function
  */
 // eslint-disable-next-line @typescript-eslint/no-redundant-type-constituents
-export type Fn = (...arg: unknown[]) => unknown | Promise<unknown>;
+export type Fn = () => unknown | Promise<unknown>;
 
 export interface FnOptions {
   /**