Create issue on security-scan instead of PR.

[harshad16]

Currently, we have a github workflow, which creates a PR.
It feel it would be more valuable to convert these into issues,
instead of creating the PR with content, as this security-scan content wouldn't help the users who rely on the Repo content.

Originally posted by @harshad16 in #404 (comment)

Action Items:

• Remove the cron and keep this workflow on demand.
• Adjust the script so that it opens Issue, instead of PR.
  • Use the resultant file to create the issue.
  • Remove the PR creation: https://github.com/opendatahub-io/notebooks/blob/main/.github/workflows/sec-scan.yml#L119-L148

[jstourac]

FTR https://issues.redhat.com/browse/RHOAIENG-6396