[docs-patrol] Clarify azure-blob-storage retry docs for managed identity token requests

Recent code changes in the repository have introduced documentation drift. The following change needs a corresponding documentation update.

## Changes Requiring Documentation Updates

### 1. `retry` docs currently overstate request coverage for managed identity auth

**Commit(s):** [`e678d02674cec3ae238e7f76890d17413b792177`](https://github.com/elastic/beats/commit/e678d02674cec3ae238e7f76890d17413b792177)

**What changed:**
- Managed identity auth was added for the Filebeat `azure-blob-storage` input.
- The implementation explicitly clears the input retry policy before creating the managed identity credential:
- `x-pack/filebeat/input/azureblobstorage/client.go:112-113` — "Any retry policy in opts is discarded"
- `x-pack/filebeat/input/azureblobstorage/client.go:120` — `opts.Retry = policy.RetryOptions{}`

**Documentation impact:**
- `docs/reference/filebeat/filebeat-input-azure-blob-storage.md:428` currently says retry settings "apply to **every** request the input makes".
- With managed identity enabled, token-endpoint requests use credential-level SDK retry behavior instead of the input `retry.*` policy.
- The `retry` section should be updated to describe this exception explicitly (for example: `retry.*` governs Azure Blob Storage data/list operations, while managed-identity token acquisition follows credential defaults).

## Suggested Actions

- [ ] Update `docs/reference/filebeat/filebeat-input-azure-blob-storage.md` (`retry` section) to document that `retry.*` does not control managed-identity token credential requests and to scope "every request" language accordingly.

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Start with docs/reference/filebeat/filebeat-input-azure-blob-storage.md around the retry section at line 428, then read x-pack/filebeat/input/azureblobstorage/client.go lines 112-120 and commit e678d02674cec3ae238e7f76890d17413b792177. Update the retry documentation to scope retry.* to Azure Blob Storage data/list operations and document the managed-identity token request exception. Done means the "every request" wording no longer overstates coverage.

Written by the indexing model from the issue text.