Removes unsupported node 6 test env, updates yarn

[AllenBW]

When yer title says it all.... doing this cuz 👉 ManageIQ/manageiq-v2v#533 (comment) 😋

[himdel]

@AllenBW maybe one more thing.. package.json still mentions 6.9.1

(we changed that to 8.9.0 for ui-classic, in ManageIQ/manageiq-ui-classic#4429)

[AllenBW]

Goooooood call, gonna do 5.10.0 for npm cuz that's whats packaged with 8.9.0

[miq-bot]

Checked commit AllenBW@580deee with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
1 file checked, 1 offense detected

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• 💣 💥 🔥 🚒 - Linter/Yaml - missing config files

[himdel]

👍 matches the same change in ui-classic

[AllenBW]

@himdel any chance we could merge this orrrr does it require more work?

[himdel]

Oh, I'd love to... but.. I guess we really need to disable the github merging limitations :(

[himdel]

@AllenBW would you object to just using the same github settings here as in ui-classic?

[AllenBW]

@himdel GOODNESS YES PLEASE DO THIS THING I don't have repo rights to fiddle with that stuff, but this thing, the requiring all checks, and checks getting stuck thing, its bitten us too many times

[himdel]

I don't have The Power either, but pinged @Fryguy :)