Modify some translation in 第一章.asciidoc

[elenacliu]

原文分别对应于 https://github.com/ethereumbook/ethereumbook/blob/develop/01what-is.asciidoc：

From a more practical perspective, Ethereum is an open source, globally decentralized computing infrastructure that executes programs called smart contracts.

As soon as you start reading about Ethereum, you will immediately encounter the term "Turing complete." Ethereum, they say, unlike Bitcoin, is Turing complete.