fix(ci): Don't sign kernel on PR (#1431)

Signed-off-by: RJ Sampson <[email protected]>

.github/workflows/reusable-build.yml

@@ -102,7 +102,7 @@ jobs:
 
       - name: Check just syntax
         uses: ublue-os/just-action@v1
-      
+
       - name: Generate tags
         id: generate-tags
         shell: bash
@@ -229,6 +229,7 @@ jobs:
 
       - name: Sign kernel
         uses: ublue-os/[email protected]
+        if: github.event_name != 'pull_request'
         with:
           image: ${{ steps.build_image.outputs.image }}
           default-tag: ${{ env.DEFAULT_TAG }}