fix(ci): skip security scan on forks to avoid SARIF upload permission error

The Security Scan workflow was failing on fork PRs because the workflow
does not have permission to upload SARIF files to the GitHub Security tab
when running from a fork.

This change adds '!github.repository.fork' checks to all steps
to prevent the workflow from running on fork repositories.

Fixes mudler#10322

Author: ghshhf

.github/workflows/secscan.yaml

@@ -15,15 +15,15 @@ jobs:
     steps:
       - name: Checkout Source
         uses: actions/checkout@v6
-        if: ${{ github.actor != 'dependabot[bot]' }}
+        if: ${{ !github.repository.fork && github.actor != 'dependabot[bot]' }}
       - name: Run Gosec Security Scanner
-        if: ${{ github.actor != 'dependabot[bot]' }}
+        if: ${{ !github.repository.fork && github.actor != 'dependabot[bot]' }}
         uses: securego/gosec@v2.27.1
         with:
           # we let the report trigger content trigger a failure using the GitHub Security features.
           args: '-no-fail -fmt sarif -out results.sarif ./...'
       - name: Upload SARIF file
-        if: ${{ github.actor != 'dependabot[bot]' }}
+        if: ${{ !github.repository.fork && github.actor != 'dependabot[bot]' }}
         uses: github/codeql-action/upload-sarif@v4
         with:
           # Path to SARIF file relative to the root of the repository