Downgrade CLI chalk dependency to install on Node v8.0.0

[bahmutov]

Similar to #6512 (execa), chalk also seems to require Node v8+ and does not install on Node v8.0.0

• https://circleci.com/gh/cypress-io/cypress-test-node-versions/10425

npm WARN deprecated request@2.88.0: request has been deprecated, see https://github.com/request/request/issues/3142

> cypress@4.0.3 postinstall /home/node/app/node_modules/cypress
> node index.js --exec install

/home/node/app/node_modules/cypress/node_modules/chalk/source/index.js:103
	...styles,
	^^^

SyntaxError: Unexpected token ...
    at createScript (vm.js:74:10)
    at Object.runInThisContext (vm.js:116:10)
    at Module._compile (module.js:533:28)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:503:32)
    at tryModuleLoad (module.js:466:12)
    at Function.Module._load (module.js:458:3)
    at Module.require (module.js:513:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (/home/node/app/node_modules/cypress/lib/util.js:22:13)

[cypress-bot]

The code for this is done in cypress-io/cypress#6569, but has yet to be released.
We'll update this issue and reference the changelog when it's released.

[cypress-bot]

Released in 4.1.0.

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