channeldb: update UpdateCommitment description

This method is only used to update the local commitment transaction.
Updated comment accordingly.

channeldb/channel.go

@@ -1239,11 +1239,11 @@ func syncNewChannel(tx *bbolt.Tx, c *OpenChannel, addrs []net.Addr) error {
 	return putLinkNode(nodeInfoBucket, linkNode)
 }
 
-// UpdateCommitment updates the commitment state for the specified party
-// (remote or local). The commitment stat completely describes the balance
-// state at this point in the commitment chain. This method its to be called on
-// two occasions: when we revoke our prior commitment state, and when the
-// remote party revokes their prior commitment state.
+// UpdateCommitment updates the local commitment state. It locks in the pending
+// local updates that were received by us from the remote party. The commitment
+// state completely describes the balance state at this point in the commitment
+// chain. This method its to be called when we revoke our prior commitment
+// state.
 func (c *OpenChannel) UpdateCommitment(newCommitment *ChannelCommitment) error {
 	c.Lock()
 	defer c.Unlock()