ci: exclude flaky connect_sandbox_async and delete_nonexistent_sandbox tests

These tests fail intermittently due to sandbox expiration (HTTP 404
ERR_NOT_FOUND) and connection errors (HTTP 0). The existing
delete_sandbox filter did not match delete_nonexistent_sandbox since
it is not a contiguous substring.

Change-Id: Id6f81e1879ec5786c39ac4312c1484b490f6c005
Co-developed-by: Claude <noreply@anthropic.com>

Author: congxiao-wxx

.github/workflows/e2e.yml

@@ -73,7 +73,7 @@ jobs:
           --ignore=tests/e2e/test_workspace_id.py \
           --ignore=tests/e2e/test_sandbox_browser.py \
           --ignore=tests/e2e/test_sandbox_code_interpreter.py \
-          -k "not (invoke or with_credential or model_proxy or process_get or delete_sandbox or connect_nonexistent or sandbox_lifecycle or connect_with_wrong_template or template_validation_code_interpreter_network)"
+          -k "not (invoke or with_credential or model_proxy or process_get or delete_sandbox or delete_nonexistent_sandbox or connect_nonexistent or connect_sandbox_async or sandbox_lifecycle or connect_with_wrong_template or template_validation_code_interpreter_network)"
 
     - name: E2E Summary
       if: always()