Removed superfluous safety check

[arkpar]

This check is a major performance hit because a tree route to the last finalized block may potentially contain thousands of blocks (as it does on kusama)
It is also unnecessary since the same condition is properly checked here:

substrate/core/client/db/src/lib.rs

Lines 897 to 904 in 7276eea

	for r in tree_route.retracted() {
	if r.hash == meta.finalized_hash {
	warn!(
	"Potential safety failure: reverting finalized block {:?}",
	(&r.number, &r.hash)
	);
	return Err(::client::error::Error::NotInFinalizedChain.into());