Update cli flag to use --format=json as --json is deprecated

[ksrb]

See ember-template-lint/ember-template-lint#2193

I think this would ideally be combined with some kind of version check to conditionally change the flag.

[patricklx]

Hi thanks for the pr.
I think you can use templateLintPackage.versionStr and just check if the first number is >= 4 to validate the version

[ksrb]

Cool if I run into a project using an older linter version than I'll look into using templateLintPackage.versionStr hopefully everyone is just using the new template linter though 🤞 .