[ricardozanini]

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Discussion or Issue link:
Fixes #1218

What this PR does:
Removes the outdated prose restriction stating $secrets can only be used in input.from. This aligns the runtime expression arguments table with the expression availability matrix and adjacent warnings, which allow $secrets across expression evaluation contexts.

Summary

 | context | `map` | The workflow's context data. |
 | input | `any` | The task's transformed input. |
 | output | `any` | The task's transformed output. |
-| secrets | `map` | A key/value map of the workflow secrets.<br>To avoid unintentional bleeding, secrets can only be used in the `input.from` runtime expression. |
+| secrets | `map` | A key/value map of the workflow secrets. |
 | authorization | [`authorizationDescriptor`](#authorization-descriptor) | Describes the resolved authorization, as defined by the task's authentication, if any. |