fix(Code Sample/PHP): update response type to be php

[mikewuu]

Not for this PR, but this really should be php

Originally posted by @razor-x in #58 (comment)

[razor-x]

@andrii-balitskyi Was the json response type for PHP intentional? Isn't there a PHP class for each resource?

[andrii-balitskyi]

@razor-x Yes, you're right, there's a class for each resource. I was referencing our current docs where we put JSON in the PHP response example. My bad.
I'm not sure how a PHP-style response should look.
Something like this looks a bit messy:
?

[razor-x]

@andrii-balitskyi For rendering the response for each language, let's use the primitive literal syntax. I realize the actual return value is a wrapper data class, but it's not possible to format that via a formatter, and it can't be copy-pasted into an interpreter.

So for PHP, this would be

[
    "connected_account_id" => "...",
    "is_managed" => True,
]