schema link missing in angular.json that was created by updating from 1.7.3 to 6-rc.2

[IgorMinar]

Versions

cli rc.2

Repro steps

• get a project built by 1.7.3
• update cli in package.json to 6.0.0-rc.2 + yarn install
• ng update @angular/cli --migrate-only --from=1.7.3

Observed behavior

angular.json is generated without the schema link:

{
  "version": 1,
  ...
}

Desired behavior

angular.json should look like this:

{
  "$schema": "./node_modules/@angular-devkit/core/src/workspace/workspace-schema.json",
  "version": 1,
  ...
}

Mention any other details that might be useful (optional)

@clydin pointed out that the upgrade code is missing the schema key: https://github.com/angular/devkit/blob/8e6c762c94de1c23bc8b53f1cb87b48726eda951/packages/schematics/angular/migrations/update-6/index.ts#L72