Fix error deprecated backstopjs

[Eduardo-Morales-Alberti]

Fix error:

waitFor is deprecated and will be removed in a future release. See https://github.com/puppeteer/puppeteer/issues/6214 for details and how to migrate your code.
Error: Evaluation failed: TypeError: n.forEach is not a function
    at Function.Z (http://apache/sites/default/files/js/js_6qryUOSwDcOZuLF_ITWgCYMA181cmiyWP1DyJzZkVkc.js:109:2092)
    at Object.m.load (http://apache/sites/default/files/js/js_6qryUOSwDcOZuLF_ITWgCYMA181cmiyWP1DyJzZkVkc.js:129:1673)
    at __puppeteer_evaluation_script__:9:29
    at ExecutionContext._evaluateInternal (/usr/local/lib/node_modules/backstopjs/node_modules/puppeteer/lib/cjs/puppeteer/common/ExecutionContext.js:221:19)
    at runMicrotasks (<anonymous>)
    at runNextTicks (internal/process/task_queues.js:60:5)
    at listOnTimeout (internal/timers.js:526:9)
    at processTimers (internal/timers.js:500:7)
    at async ExecutionContext.evaluate (/usr/local/lib/node_modules/backstopjs/node_modules/puppeteer/lib/cjs/puppeteer/common/ExecutionContext.js:110:16)

Related issue: puppeteer/puppeteer#6214