chore: disable PEER_DISCOVERY by default for mainnet

PEER_DISCOVERY is now disabled by default for mainnet deployments
to reduce unnecessary peer discovery is still in beta version. It remains enabled
for preprod environments where dynamic peer discovery is less risky.

Changes:
- Set PEER_DISCOVERY=false in .env.docker-compose (mainnet)
- Preprod configurations keep PEER_DISCOVERY=true

Author: Mateusz Czeladka

.env.docker-compose

@@ -109,7 +109,7 @@ CONTINUE_PARSING_ON_ERROR=true
 SYNC=true
 
 ## Peer Discovery
-PEER_DISCOVERY=true
+PEER_DISCOVERY=false
 
 ## Token Registry
 TOKEN_REGISTRY_ENABLED=false