Dashboards: Add missing system color field

[joselcvarela]

Description

When trying to apply a schema this change appears every time:

Fields:
  - Delete directus_dashboards.color

Be debugging a little I found that column color was added to directus_dashboards table, but is not specified on system fields (yaml files):
https://github.com/directus/directus/blob/fix/missing-dashboard-field/api/src/database/migrations/20220429B-add-color-to-insights-icon.ts#L10

This cause the schema to be applied wrongly.

Type of Change

• Bugfix
• New Feature
• Refactor / codestyle updates
• Other, please describe:

Requirements Checklist

• New / updated tests are included
• All tests are passing locally
• Performed a self-review of the submitted code

If adding a new feature:

• Documentation was added/updated