benchmark: increase iteration number to appropriate one

Increase the iteration number from 500 to 2500 to make time consumption
of crypto operation dominate the benchmark running.

Fixes: nodejs#50571

benchmark/crypto/aes-gcm-throughput.js

@@ -3,7 +3,7 @@ const common = require('../common.js');
 const crypto = require('crypto');
 const keylen = { 'aes-128-gcm': 16, 'aes-192-gcm': 24, 'aes-256-gcm': 32 };
 const bench = common.createBenchmark(main, {
-  n: [500],
+  n: [2500],
   cipher: ['aes-128-gcm', 'aes-192-gcm', 'aes-256-gcm'],
   len: [1024, 4 * 1024, 16 * 1024, 64 * 1024, 256 * 1024, 1024 * 1024],
 });