docs: Add note that Server Actions work with static routes (#55626)
In the new next.js v13.5 blog post, the [other improvements section](https://nextjs.org/blog/next-13-5#other-improvements) mentions:
> [Improvement] Server Actions now work with fully static routes (including revalidating data with ISR)
In the forms and mutation docs page, the [good to know section](https://nextjs.org/docs/app/building-your-application/data-fetching/forms-and-mutations#how-server-actions-work) mentions:
> Currently, if a route uses a Server Action, it is required to [render dynamically](https://nextjs.org/docs/app/building-your-application/rendering/server-components#server-rendering-strategies).
I have changed the good to know section to convey the new improvement mentioned in the v13.5 blog post