fix env example [skip ci]

Author: erhant

.env.example

@@ -7,10 +7,6 @@ DKN_WALLET_SECRET_KEY=
 DKN_MODELS=
 # P2P address, you don't need to change this unless this port is already in use.
 DKN_P2P_LISTEN_ADDR=/ip4/0.0.0.0/tcp/4001
-# Comma-separated static relay nodes
-DKN_RELAY_NODES=
-# Comma-separated static bootstrap nodes
-DKN_BOOTSTRAP_NODES=
 # Batch size for task worker, you do not need to edit this.
 DKN_BATCH_SIZE=
 
@@ -28,10 +24,6 @@ OPENAI_API_KEY=
 GEMINI_API_KEY=
 ## Open Router (if used, required) ##
 OPENROUTER_API_KEY=
-## Serper (optional) ##
-SERPER_API_KEY=
-## Jina (optional) ##
-JINA_API_KEY=
 
 ## Log levels
 RUST_LOG=none