cleanup: remove unnecessary require for global Buffer

[Phillip9587]

The Buffer object is globally available in Node.js, so there is no need to explicitly require it.

[wesleytodd]

Can we update the history.md file? Sorry for being pedantic, but until we automate it I want to make sure we dont miss something in the release notes on accident.

[Phillip9587]

@wesleytodd Does this require an entry in HISTORY.md? The changes don't alter any behavior; they simply remove unnecessary requires of the global buffer.

Edit: I just read your comment on #6147 and #6176 and just added the entry

[wesleytodd]

Thanks! yeah we will be automating that, but I think there is some question still of how deep we want to go on the automation, so it has not happened yet. Just making sure we don't make a mistake by abandoning the process even if it is a bad process 😄 .