fix(types): defaultActiveKey to NavProps in Nav.d.ts (#3638)

Open issue #3623

The [documentation for the Nav component](https://react-bootstrap.netlify.com/components/navs) lists `defaultActiveKey` as a supported property.

In this case I didn't add a specific type for Typescript but instead just used the existing type for `activeKey` from `NavProps`. This matches the typing of `Tab.d.ts`

types/components/Nav.d.ts

@@ -10,6 +10,7 @@ export interface NavProps {
   cardHeaderBsPrefix?: string;
   variant?: 'tabs' | 'pills';
   activeKey?: unknown;
+  defaultActiveKey?: unknown;
   fill?: boolean;
   justify?: boolean;
   onSelect?: SelectCallback;