chore: correct Spanner instance reference for ITs (#781)

* chore: correct Spanner instance reference for ITs

Fixes #778.

* Update pom.xml

* Update integration.cfg

* Update owlbot.py

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Co-authored-by: Neenu Shaji <[email protected]>
Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: 3 people

owlbot.py

@@ -21,4 +21,5 @@
     '.github/release-please.yml',
     '.github/sync-repo-settings.yaml',
     '.github/blunderbuss.yml',
+    '.kokoro/nightly/integration.cfg'
 ])