springboot upgrade netty to 4.1.47.Final

refer: Netty 4.1.47.Final released

Comment From: pivotal-issuemaster

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Comment From: pivotal-issuemaster

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Comment From: snicoll

@m1ngyuan thanks for the PR but we don't need one for dependencies upgrade like this (see the note in the PR template). We have a tool that perform this semi-automatically and we'll apply it un due course.