Merge bitcoin/bitcoin#27072: doc: Remove unused REVIEWERS file

fa8e3aa doc: Remove unused REVIEWERS file (721217.xyz)

Pull request description:

  Unused for way more than two months after bitcoin/bitcoin#25613 (comment)

  See also maflcko/DrahtBot@bb5ebad

ACKs for top commit:
  sipa:
    ACK fa8e3aa
  john-moffett:
    ACK fa8e3aa

Tree-SHA512: def650d34f04abd18e37cf19b5df34463157a99fbb537c4c98092c8312eb2a572ccde13ec5374f3b9e7cb90cef220cfe07f4522ffbfeb9407b20b3ada1d7706c

Author: bitcoin-core-merge-script