fix: Explicitly allow undefined type for table.type.summary

Closes storybookjs/storybook#27129

Allowing explicitly undefined as type for table.type.summary lets Story
authors disable the automatic type summary while having strict
TypeScript options. With exactOptionalPropertyTypes enforced, using
undefined as a type was forbidden, as TypeScript would raise an error.
With this change, it should be allowed.

src/story.ts

@@ -156,7 +156,7 @@ export interface InputType {
     /**
      * @see https://storybook.js.org/docs/api/arg-types#tabletype
      */
-    type?: { summary?: string; detail?: string };
+    type?: { summary?: string | undefined; detail?: string };
   };
   /**
    * @see https://storybook.js.org/docs/api/arg-types#type