benchmark: remove redundant timers benchmark

The immediate.js benchmark with `type` set to `depth` measures the same
thing as set-immediate-depth.js. Remove the redundancy.`

PR-URL: https://github.com/nodejs/node/pull/13009
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>

benchmark/timers/set-immediate-depth.js

@@ -1,22 +0,0 @@
-'use strict';
-
-const common = require('../common.js');
-const bench = common.createBenchmark(main, {
-  millions: [10]
-});
-
-function main(conf) {
-  const N = +conf.millions * 1e6;
-  let n = N;
-
-  process.on('exit', function() {
-    bench.end(N / 1e6);
-  });
-
-  bench.start();
-  setImmediate(onNextTick);
-  function onNextTick() {
-    if (--n)
-      setImmediate(onNextTick);
-  }
-}