refactor: Updated all Svelte fetch data examples to use #await block.

[kotikkir9]

While reading 'fetch data' examples, I noticed that the current Svelte snippets do not use the #await block, which provides native Svelte functionality for dealing with promises inside the markup. My PR behaves exactly the same as before; it just makes the code simpler and smaller, using native Svelte functionality.

[matschik]

It would work well with await block but when comparing frameworks, comparing await block with the other implementations can be harder. We already got some proposals to use await block but making easy to compare it more important for the purpose Component Party.

[Thiagolino8]

Comparing await block with the other implementations can be harder

Why isn't this the case with solid-js, which is using its own API to handle promises?

Making easy to compare it more important for the purpose Component Party

From what I understood, the purpose of component party was to show the differences between frameworks. If the specific capabilities of the frameworks aren't used, it ends up being a tutorial on how to use vanilla js in frameworks.