[gardening] SkipSlow dart/regress_52703_test in hot-reload test mode

The test is flakily timing out in hot-reload test mode.

Issue #52784

TEST=ci

Change-Id: I466e1997aa691921d38a672f293b2a7e97df36aa
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/312904
Reviewed-by: Daco Harkes <[email protected]>
Commit-Queue: Martin Kustermann <[email protected]>

Author: mkustermann

runtime/tests/vm/vm.status

@@ -374,6 +374,7 @@ dart/heapsnapshot_cli_test: SkipSlow
 dart/isolates/reload_many_isolates_live_and_die_test: SkipSlow # The test itself does reloading of subprocesses.
 dart/kernel_determinism_test: SkipSlow
 dart/regress_48196_test: SkipSlow
+dart/regress_52703_test: SkipSlow
 dart_2/data_uri_spawn_test: Skip # Timeout
 dart_2/heap_snapshot_referrers_test: SkipSlow
 dart_2/heapsnapshot_cli_test: SkipSlow