turns down logging output to debug (#4032)

Signed-off-by: Justin Florentine <justin+github@florentine.us>

ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/SyncTargetManager.java

@@ -82,7 +82,7 @@ public abstract class SyncTargetManager {
                             return waitForPeerAndThenSetSyncTarget();
                           }
                           final SyncTarget syncTarget = new SyncTarget(bestPeer, target);
-                          LOG.info(
+                          LOG.debug(
                               "Found common ancestor with peer {} at block {}",
                               bestPeer,
                               target.getNumber());