Remove duplicated coinbase CDP options in .env.example

The removed section is identical to the section above it.

Author: juntao

.env.example

@@ -156,14 +156,6 @@ ZEROG_EVM_RPC=
 ZEROG_PRIVATE_KEY=
 ZEROG_FLOW_ADDRESS=
 
-# Coinbase
-COINBASE_COMMERCE_KEY=
-COINBASE_API_KEY=
-COINBASE_PRIVATE_KEY=
-
-COINBASE_GENERATED_WALLET_ID=
-COINBASE_GENERATED_WALLET_HEX_SEED=
-
 # TEE Configuration
 DSTACK_SIMULATOR_ENDPOINT=
 WALLET_SECRET_SALT= # ONLY DEFINE IF YOU WANT TO USE TEE Plugin, otherwise it will throw errors