DOCS - Incorrect documentation on pre-upgrade checker configuration

[xorinzor]

I didn't know what Issue category it would fall under, so I'll just put it here.

The documentation for installing with ArgoCD seems outdated. The values makes use of helmPreUpgradeCheckerJob.enabled: false whereas this has changed to preUpgradeChecker.jobEnabled: false in 1.6.0+.

Old documentation can be read in step 3, here.

This has been noted in issue #6415 and commented on by 2 others, but doesn't appear to have triggered any action.

[derekbit]

cc @yangchiu @mantissahz

[innobead]

@derekbit Let's convert this to an issue and assign to @yangchiu . Thanks.

[mantissahz]

@derekbit I have converted this to an issue.