[serve] deflake test_serve_dashboard (#46535)

linux://python/ray/dashboard:test_serve_dashboard has become timedout
and flaky recently (#46459);
not sure if it has anything to do with
#45943. I just increase its timed
out in this PR

Test:
- CI
- https://buildkite.com/ray-project/postmerge/builds/5358

Signed-off-by: can <[email protected]>

python/ray/dashboard/BUILD

@@ -99,7 +99,7 @@ py_test(
 
 py_test(
     name = "test_serve_dashboard",
-    size = "large",
+    size = "enormous",
     srcs = ["modules/serve/tests/test_serve_dashboard.py"],
     tags = ["team:serve"],
     deps = [":conftest"],