benchmark: increase get-ciphers iteration number to appropriate one

Increase the iteration number from 5000 to 500000 to make time
consumption of crypto operation dominate the benchmark running.

Fixes: nodejs#50571

benchmark/crypto/get-ciphers.js

@@ -3,7 +3,7 @@
 const common = require('../common.js');
 
 const bench = common.createBenchmark(main, {
-  n: [1, 5000],
+  n: [1, 500000],
   v: ['crypto', 'tls'],
 });