docs(changeset): clarify mapping.errorPolicy is unrelated to the retry convergence

#4664 retires `mapping.errorPolicy` in the same 17.0.0 window and its values
included 'retry', so a reader could plausibly assume it migrates into a
`retryPolicy` block. It does not — different type, inert enum, and its own
prescription points at the import REQUEST's options.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01M9uWvoEp9CoLzYjNExj9sL

Author: claude

.changeset/retry-policy-dual-source-c8.md

@@ -68,6 +68,14 @@ ever faster, the opposite of backoff.
 shape** (every key optional) rather than the post-parse shape. Use the new
 `RetryPolicyParsed` where you need defaults applied.
 
+## Not related to `mapping.errorPolicy` (#4509 / #4664, same release)
+
+17.0.0 also retires `mapping.errorPolicy`, whose values included `'retry'`. That is a
+different thing on a different type: an inert enum on the stored **mapping**, whose
+prescription is "error handling on the import path belongs to the import REQUEST's own
+options". It does **not** migrate to a `retryPolicy` block, and nothing in this change
+affects it.
+
 ## What you gain
 
 `job.retryPolicy` accepts **`maxRetryDelayMs`** (ceiling on a single backoff delay) and