Use function declaration for WithApolloClient example

[charpeni]

While reading through the docs, I noticed two things.

• We don't need to import react here and aren't doing it in other places, let's unclutter the example.
• We are using function declarations everywhere for React components except for this WithApolloClient component, which could be confusing as the example doesn't need an arrow function.

Checklist:

• If this PR is a new feature, please reference an issue where a consensus about the design was reached (not necessary for small changes)
• Make sure all of the significant new logic is covered by tests

[jpvajda]

@charpeni Thanks for the PR and catching this inconsistency in our Docs! 🥳