fix: add comment to make it clear what the variable is used for

.env.example

@@ -160,7 +160,7 @@ COINBASE_GENERATED_WALLET_HEX_SEED=
 
 # TEE Configuration
 DSTACK_SIMULATOR_ENDPOINT=
-WALLET_SECRET_SALT=
+WALLET_SECRET_SALT= # ONLY DEFINE IF YOU WANT TO USE TEE Plugin, otherwise it will throw errors
 
 # Galadriel Configuration
 GALADRIEL_API_KEY=gal-* # Get from https://dashboard.galadriel.com/