[gardening] Clean up list of stress tests.

Remove accidently added test file added in https://dart.googlesource.com/sdk/+/327d7df4689b0531f2ee1ff24019d62ba7534418

Change-Id: I8ef6df14d5380c3e8ee4d62ea6682f15f66c5ddf
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/337288
Reviewed-by: Liam Appelbe <liama@google.com>
Commit-Queue: Alexander Aprelev <aam@google.com>

runtime/tests/concurrency/stress_test_list.json

@@ -32,7 +32,6 @@
   "../vm/dart/double_hash_code_double_values_test.dart",
   "../vm/dart/double_materialize_test.dart",
   "../vm/dart/double_to_smi_test.dart",
-  "../vm/dart/elide_store_instance_test.dart",
   "../vm/dart/error_stacktrace_test.dart",
   "../vm/dart/exported_symbols_test.dart",
   "../vm/dart/extension_names_test.dart",