ci: bug_snapshot: Restrict to zephyrproject-rtos organisation

This commit restricts the bug snapshot workflow to the
`zephyrproject-rtos` organisation because it requires access to the
project internal infrastructure and cannot be reused downstream.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

.github/workflows/bug_snapshot.yaml

@@ -17,6 +17,7 @@ jobs:
   make_bugs_pickle:
     name: Make bugs pickle
     runs-on: ubuntu-latest
+    if: github.repository_owner == 'zephyrproject-rtos'
 
     steps:
     - name: Checkout