bug: flaky integration test `tests_integ/memory/integrations/test_session_manager.py::TestAgentCoreMemorySessionManager:`

[Hweinstock]

Problem

Failed run on unrelated PR: https://github.com/aws/bedrock-agentcore-sdk-python/actions/runs/27363971772/job/80858495079?pr=513

Definition of Done

• implement additional guardrails against the noisy this flaky test generates.(retries already exist).