tests: Run "test_live_upgrade_numa" on aarch64 only

Our Azure VM for x86_64 workers are now much smaller, and does not have
enough RAM to run the "test_live_upgrade_numa" test. Instead, this test
will still be tested on the aarch64 worker, and the "local" upgrade
variation of the same test will also be tested on all workers. So we
should be good from test coverage point of view.

Signed-off-by: Bo Chen <chen.bo@intel.com>

tests/integration.rs

@@ -9606,6 +9606,7 @@ mod live_migration {
         }
 
         #[test]
+        #[cfg(target_arch = "aarch64")] // see: #6272
         #[cfg(not(feature = "mshv"))]
         fn test_live_upgrade_numa() {
             _test_live_migration_numa(true, false)