Sync retryable reads with SDAM

[prestonvasquez]

This PR proposes a re-phrasing of the "Why are read operations only retried once by default?" section of retryable reads to fix inconsistencies between the retryable reads and SDAM specifications. From the retryable reads Q&A on why read operations are only retried once:

In the case of a transient error, the driver will mark the server as “unknown” per the SDAM spec.

From the SDAM rationale for “Other transient errors” :

There are other transient errors a server may return, e.g. retryable errors listed in the retryable writes spec. SDAM does not consider these because they do not imply the connected server should be marked as “Unknown”.

• Update changelog.
  - [ ] Make sure there are generated JSON files from the YAML test files.
  - [ ] Test changes in at least one language driver.
  - [ ] Test these changes against all server versions and topologies (including standalone, replica set, sharded clusters, and serverless).

[ShaneHarvey]

Thanks Preston!