[QE] Remove all deprecated code in test/upgrade package

[cardil]

Remove all deprecated code in test/upgrade package introduced by #5321 and #4815. Example:

eventing/test/upgrade/prober/configuration.go

Line 53 in 14ae489

// TODO(ksuszyns): Remove this val in next release

Other places:

test/upgrade/prober/prober.go:38:// TODO(ksuszyns): Remove this interface in next release
test/upgrade/prober/prober.go:126:// TODO(ksuszyns): Remove this func in next release
test/upgrade/prober/prober.go:142:// TODO(ksuszyns): Remove this func in next release
test/upgrade/prober/configuration.go:53:	// TODO(ksuszyns): Remove this val in next release
test/upgrade/prober/configuration.go:71:	// TODO(ksuszyns): Remove this opt in next release
test/upgrade/prober/configuration.go:75:	// TODO(ksuszyns): Remove this opt in next release
test/upgrade/prober/configuration.go:119:// TODO(ksuszyns): Remove this func in next release
test/upgrade/prober/configuration.go:166:	// TODO(ksuszyns): Remove this block in next release

/assign
/area test-and-release