add GP3_THROUGHPUT .env

Author: Simon Goldberg

lib/bitcoin-core/sample-configs/.env-sample-bitcoin-mainnet

@@ -17,4 +17,5 @@ ASG_DESIRED_CAPACITY=2
 
 # The following configuration has been tested and proven effective for a Bitcoin Core node to achieve full synchronization without incurring additional costs:
 GP3_IOPS=3000
+GP3_THROUGHPUT=125
 CPU_ARCHITECTURE=X86_64 # Options: X86_64 or ARM64