[gardening] Remove raw_datagram_read_all_test from isolate stress test list.

The test has hardcoded timing expectations which don't seem to work reliably in isolate stress test setting.

Fixes #46982
TEST=ci

Change-Id: I557a22e897d6c61994755e02f9d8ead41f7407fa
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/458940
Reviewed-by: Brian Quinlan <[email protected]>
Commit-Queue: Alexander Aprelev <[email protected]>

Author: aam

runtime/tests/concurrency/stress_test_list.json

@@ -3502,7 +3502,6 @@
   "../../../tests/standalone/io/process_pid_test.dart",
   "../../../tests/standalone/io/process_segfault_test.dart",
   "../../../tests/standalone/io/process_start_exception_test.dart",
-  "../../../tests/standalone/io/raw_datagram_read_all_test.dart",
   "../../../tests/standalone/io/raw_datagram_zero_length_test.dart",
   "../../../tests/standalone/io/raw_server_socket_cancel_test.dart",
   "../../../tests/standalone/io/raw_socket_typed_data_test.dart",