fix: patching algopy import syntax in hello world

[aorumbayev]

Proposed Changes

• Fix algopy import syntax

[achidlow]

This an okay change to make, but it's not just a syntax change between using algopy.arc4.String and algopy.String, it will change the byte code (probably for the better).

I'd keep the from algopy import arc4 though, rather than from algopy.arc4 import xyz, this is especially helpful to see at a glance where ARC-4 types are being used vs native, especially in the case the classes have the same names like String and UInt64