3.9.1

• bump botocore dependency specification to support
  "botocore >= 1.43.66, < 1.43.76" (#1693, #1709)
• seed the amz-sdk-request header's max token on the initial request
  attempt (previously only appeared once a retry occurred) and honour a
  per-request read_timeout override when computing retry timing, matching
  botocore 1.43.66 and 1.43.72 (#1709)
• fix login credential refreshes calling botocore's sync-only
  create_o_auth2_token compatibility alias, which aiobotocore cannot
  resolve asynchronously, by calling the generated create_oauth2_token
  method directly (closes #1697) (#1704)
• fix a concurrency-safety issue in HTTPSession session management
  (closes #1695) (#1696)