Doc: Add clarity to WorkflowIdReusePolicy for server behavior (#559)

<!-- Describe what has changed in this PR -->
**What changed?**
Add a little more clarity that this is the server/client behavior, not
SDK behavior.

<!-- Tell your future self why have you made these changes -->
**Why?**
There was feedback that this could use more clarity.
temporalio/sdk-go#1857

<!-- Are there any breaking changes on binary or code level? -->
No, comment only change

Author: yuandrew

Diff for: openapi/openapiv2.json

@@ -14752,7 +14752,7 @@
         "WORKFLOW_ID_REUSE_POLICY_TERMINATE_IF_RUNNING"
       ],
       "default": "WORKFLOW_ID_REUSE_POLICY_UNSPECIFIED",
-      "description": "Defines whether to allow re-using a workflow id from a previously *closed* workflow.\nIf the request is denied, a `WorkflowExecutionAlreadyStartedFailure` is returned.\n\nSee `WorkflowIdConflictPolicy` for handling workflow id duplication with a *running* workflow.\n\n - WORKFLOW_ID_REUSE_POLICY_ALLOW_DUPLICATE: Allow starting a workflow execution using the same workflow id.\n - WORKFLOW_ID_REUSE_POLICY_ALLOW_DUPLICATE_FAILED_ONLY: Allow starting a workflow execution using the same workflow id, only when the last\nexecution's final state is one of [terminated, cancelled, timed out, failed].\n - WORKFLOW_ID_REUSE_POLICY_REJECT_DUPLICATE: Do not permit re-use of the workflow id for this workflow. Future start workflow requests\ncould potentially change the policy, allowing re-use of the workflow id.\n - WORKFLOW_ID_REUSE_POLICY_TERMINATE_IF_RUNNING: This option belongs in WorkflowIdConflictPolicy but is here for backwards compatibility.\nIf specified, it acts like ALLOW_DUPLICATE, but also the WorkflowId*Conflict*Policy on\nthe request is treated as WORKFLOW_ID_CONFLICT_POLICY_TERMINATE_EXISTING.\nIf no running workflow, then the behavior is the same as ALLOW_DUPLICATE."
+      "description": "Defines whether to allow re-using a workflow id from a previously *closed* workflow.\nIf the request is denied, the server returns a `WorkflowExecutionAlreadyStartedFailure` error.\n\nSee `WorkflowIdConflictPolicy` for handling workflow id duplication with a *running* workflow.\n\n - WORKFLOW_ID_REUSE_POLICY_ALLOW_DUPLICATE: Allow starting a workflow execution using the same workflow id.\n - WORKFLOW_ID_REUSE_POLICY_ALLOW_DUPLICATE_FAILED_ONLY: Allow starting a workflow execution using the same workflow id, only when the last\nexecution's final state is one of [terminated, cancelled, timed out, failed].\n - WORKFLOW_ID_REUSE_POLICY_REJECT_DUPLICATE: Do not permit re-use of the workflow id for this workflow. Future start workflow requests\ncould potentially change the policy, allowing re-use of the workflow id.\n - WORKFLOW_ID_REUSE_POLICY_TERMINATE_IF_RUNNING: This option belongs in WorkflowIdConflictPolicy but is here for backwards compatibility.\nIf specified, it acts like ALLOW_DUPLICATE, but also the WorkflowId*Conflict*Policy on\nthe request is treated as WORKFLOW_ID_CONFLICT_POLICY_TERMINATE_EXISTING.\nIf no running workflow, then the behavior is the same as ALLOW_DUPLICATE."
     },
     "v1WorkflowPropertiesModifiedEventAttributes": {
       "type": "object",

Diff for: temporal/api/enums/v1/workflow.proto

@@ -32,7 +32,7 @@ option ruby_package = "Temporalio::Api::Enums::V1";
 option csharp_namespace = "Temporalio.Api.Enums.V1";
 
 // Defines whether to allow re-using a workflow id from a previously *closed* workflow.
-// If the request is denied, a `WorkflowExecutionAlreadyStartedFailure` is returned.
+// If the request is denied, the server returns a `WorkflowExecutionAlreadyStartedFailure` error.
 //
 // See `WorkflowIdConflictPolicy` for handling workflow id duplication with a *running* workflow.
 enum WorkflowIdReusePolicy {