docs: suggested quickstart downloads don't exist anymore

[marcoderama]

The page https://docs.kalix.io/javascript/quickstart/sc-eventsourced-entity-javascript.html contains a Note that says

The shopping-cart-javascript quickstart no longer exists. I believe that should be shopping-cart-javascript-protobuf now.

And while we're at it, the same applies to the customer-registry example. That should reference customer-registry-javascript-protobuf instead of customer-registry-javascript now.

Digging some more, the same is true for the typescript references here and here.

And finally, it looks like even those changes won't quite work cuz it looks like one of the typescript quickstart files is incorrectly named:

$ kalix quickstart list | grep customer-registry-typescript
customer-registry-typescripti-protobuf   Customer Registry              typescript/protobuf   customer-registry 

Notice the typescripti in there...