Correct sequence diagram

Author: emhane

discv5/discv5-theory.md

@@ -536,11 +536,15 @@ containers, these are abbreviated in the sequence diagram below as follows:
 
 ```mermaid
     sequenceDiagram
+        participant Alice
+        participant Relay
+        participant Bob
+        
         Relay-->>Alice: m(NODES[Bob's ENR])
-        Alice->Bob: m(nonce,FINDNODE)
+        Alice->>Bob: m(nonce,FINDNODE)
         Note left of Alice:Hole punched in Alice's NAT for Bob
-        Alice->Relay: n(RELAYINIT[nonce])
-        Relay->Bob:n(RELAYMSG[nonce])
+        Alice->>Relay: n(RELAYINIT[nonce])
+        Relay->>Bob:n(RELAYMSG[nonce])
         Bob-->>Alice: whoareyou(nonce)
         Note right of Bob: Hole punched in Bob's NAT for Alice
 ```