Fix workflow validation logic

[dogancanbakir]

Proposed changes

Closes #5686

$ cat test_workflow.yaml 
id: kev-workflow

info:
  name: KEV Workflow
  description: This workflow runs the relevant Nuclei templates to detect Known Exploited Vulnerabilities.
workflows:
  - tags: kev

$  go run . -w test_template.yaml -validate

                     __     _
   ____  __  _______/ /__  (_)
  / __ \/ / / / ___/ / _ \/ /
 / / / / /_/ / /__/ /  __/ /
/_/ /_/\__,_/\___/_/\___/_/   v3.3.5

                projectdiscovery.io

[VER] Started metrics server at localhost:9092
[ERR] Error occurred parsing template ../test_workflow.yaml: [invalid template:RUNTIME] no template author field provided
[FTL] Could not validate templates: errors occurred during template validation
exit status 1

Checklist

• Pull request is created against the dev branch
• All checks passed (lint, unit/integration/regression tests etc.) with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)