benchmark: remove duplicate ffi add-64 benchmark

add-64.js measured the same add_f64 symbol with the same signature as
add-f64.js and differed only in its argument constants.

Signed-off-by: Soul Lee <alus20x@gmail.com>
PR-URL: https://github.com/nodejs/node/pull/66121
Refs: https://github.com/nodejs/node/pull/63068
Refs: https://github.com/nodejs/node/pull/62918
Reviewed-By: Daeyeon Jeong <daeyeon.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

benchmark/ffi/add-64.js

@@ -1,26 +0,0 @@
-'use strict';
-
-const common = require('../common.js');
-const ffi = require('node:ffi');
-const { libraryPath, ensureFixtureLibrary } = require('./common.js');
-
-const bench = common.createBenchmark(main, {
-  n: [1e7],
-});
-
-ensureFixtureLibrary();
-
-const { lib, functions } = ffi.dlopen(libraryPath, {
-  add_f64: { return: 'f64', arguments: ['f64', 'f64'] },
-});
-
-const add = functions.add_f64;
-
-function main({ n }) {
-  bench.start();
-  for (let i = 0; i < n; ++i)
-    add(20.5, 21.5);
-  bench.end(n);
-
-  lib.close();
-}