fix: Only run nightly-publish-ci for deephaven project (deephaven#5943)

Author: devinrsmith

.github/workflows/nightly-publish-ci.yml

@@ -12,6 +12,7 @@ concurrency:
 jobs:
   nightly-publish:
     runs-on: ubuntu-24.04
+    if: ${{ github.repository_owner == 'deephaven' }}
 
     steps:
       - name: Checkout