[core] disable asan tests on premerge (#51772)

currently failing

Signed-off-by: Lonnie Liu <lonnie@anyscale.com>

Author: aslonnie

.buildkite/core.rayci.yml

@@ -214,7 +214,9 @@ steps:
         --except-tags kubernetes,manual
 
   - label: ":ray: core: asan tests"
-    tags: python
+    tags:
+      - python
+      - skip-on-premerge # currently failing
     instance_type: medium
     commands:
       - bazel run //ci/ray_ci:test_in_docker -- //python/ray/tests/... core