fix(schema): allow environment.deployment boolean

[Solaris-star]

Summary

Fixes #6086.

GitHub Actions added environment.deployment so workflows can use an environment without creating a deployment:

jobs:
  example:
    runs-on: ubuntu-latest
    environment:
      name: production
      deployment: false

Act's strict schema (job-environment-mapping) only allowed name and url, so act --validate --strict failed with Unknown Property deployment.

Changes

• Add deployment (boolean) to pkg/schema/workflow_schema.json
• Schema unit tests for deployment: true and deployment: false

Test plan

go test ./pkg/schema/ -count=1
# ok