eth/downloader: remove eth62 (#21378)

* init

notes

removed some mentions of eth62, bumped protocol err too old to >=63

* remove sanity checks and bump supported protocol version up to 63

* remove 62 tests, still need to add 65

* remove 65 tests
# Conflicts:
#	eth/downloader/downloader_test.go
#	eth/downloader/peer.go