chore(security-guardian): skip release and mergeback PRs (#34454)

### Issue # (if applicable)

Closes #<issue number here>.
An issue where skipping release and merge back PRs dint work because this code just skips the step
```
run: echo "Skipping Security Guardian for release PR" && exit 0 
```
### Reason for this change



### Description of changes



### Describe any new or updated permissions being added
N/A



### Description of how you validated changes



### Checklist
- [ x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: QuantumNeuralCoder

.github/workflows/security-guardian.yml

@@ -3,21 +3,23 @@ on:
   pull_request: {}
 
 jobs:
+  log-skip:
+    if: |
+      startsWith(github.event.pull_request.title, 'chore(release):') ||
+      startsWith(github.event.pull_request.title, 'chore(merge-back):')
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo "Skipping Security Guardian for release/merge-back PR"
   run-security-guardian:
+    if: |
+      !startsWith(github.event.pull_request.title, 'chore(release):') &&
+      !startsWith(github.event.pull_request.title, 'chore(merge-back):')
     runs-on: ubuntu-latest
     steps:      
-      - name: Skip check for release PRs
-        if: |
-            (
-              startsWith(github.event.pull_request.title, 'chore(release):') ||
-              startsWith(github.event.pull_request.title, 'chore(merge-back):')
-            )
-        run: echo "Skipping Security Guardian for release PR" && exit 0
-
       - name: Checkout
         uses: actions/checkout@v4
         with:
-          fetch-depth: 0  # Required to enable full git diff
+          fetch-depth: 0  
 
       - name: Install cfn-guard
         run: |