ci: only run `aio_preview` job on PR builds (#26030)

There can be no preview on non-PR builds, so there is no point in
running the job.

PR Close #26030

.circleci/config.yml

@@ -140,6 +140,7 @@ jobs:
       - *setup_bazel_remote_execution
       - run: bazel query --output=label //... | xargs bazel test --define=compile=local --build_tag_filters=ivy-local --test_tag_filters=-manual,ivy-local
 
+  # This job should only be run on PR builds, where `CIRCLE_PR_NUMBER` is defined.
   aio_preview:
     <<: *job_defaults
     environment:
@@ -251,7 +252,11 @@ workflows:
       - test_ivy_jit
       - test_ivy_aot
       - build-packages-dist
-      - aio_preview
+      - aio_preview:
+          # Only run on PR builds. (There can be no previews for non-PR builds.)
+          filters:
+            branches:
+              only: /pull\/\d+/
       - integration_test:
           requires:
             - build-packages-dist
@@ -280,6 +285,7 @@ workflows:
             branches:
               only:
                 - master
+
 notify:
   webhooks:
     - url: https://ngbuilds.io/circle-build