Update .github/workflows/docker-jupyter-image.yml

was there only for testing on all branches

Co-authored-by: ElliottKasoar <45317199+ElliottKasoar@users.noreply.github.com>

Author: alinelena

.github/workflows/docker-jupyter-image.yml

@@ -1,12 +1,12 @@
 name: ghcr-jupyter
 on:
   push:
-#    branches: [ "main" ]
-#  pull_request:
-#    branches: [ "main" ]
+    branches: [ "main" ]
+
 jobs:
   build:
     runs-on: ubuntu-latest
+    if: github.repository == 'stfc/janus-core'
     permissions:
       packages: write
       contents: read