github actions: Switch to multiline string format suggested by GA docs

The validate-kernel-commits github action has the following errors:

    Error: Process completed with exit code 1.
    Error: Unable to process file command 'output' successfully.
    Error: Invalid value. Matching delimiter not found ''EOF''

Switch to the multiline string format suggested in the github action
documentation here:
https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-commands#example-of-a-multiline-string

Author: bmastbergen

.github/workflows/validate-kernel-commits.yml

@@ -184,9 +184,11 @@ jobs:
           FILTERED_OUTPUT=$(echo "$OUTPUT" | grep -v "jira-user\|jira-key\|basic_auth\|Authorization\|$JIRA_API_TOKEN")
 
           echo "$FILTERED_OUTPUT"
-          echo "output<<'EOF'" >> $GITHUB_OUTPUT
-          echo "$FILTERED_OUTPUT" >> $GITHUB_OUTPUT
-          echo "EOF" >> $GITHUB_OUTPUT
+          {
+            echo "output<<EOF"
+            echo "$FILTERED_OUTPUT"
+            echo "EOF"
+          } >> $GITHUB_OUTPUT
 
           # Check if there are any issues based on output patterns
           if echo "$FILTERED_OUTPUT" | grep -q "❌ Errors:"; then