fixed typo HMCA --> HMAC

routing.asciidoc

@@ -600,7 +600,7 @@ Some - but not all - of the reasons for errors could be:
 * A node does not have enough liquidity to set up the next HTLC
 * The next payment channel does not exist anymore as it might have been closed while the onion was being routed to the node which was supposed to forward the onion along its channel.
 * While the channel might still be open - as the funding transaction was never spent - it might happen that the other peer is offline. This of course prevents the node to forward the onion.
-* The key exchanges of the sender might have been wrong so the decryption of the onion failed or the HMCAs do not match. (also in case someone tried to tamper with the onion)
+* The key exchanges of the sender might have been wrong so the decryption of the onion failed or the HMACs do not match. (also in case someone tried to tamper with the onion)
 * The recipient might not have issued an invoice and does not know the payment details.
 * The amount of the final HTLC is too low and the recipient does not want to release the preimage.