False positives when readOnly property using referenced enum

**Describe the bug**

I'm working on https://github.com/Azure/azure-rest-api-specs-pr/pull/15631 and there are a lot of false positives with a message of `The read only property has changed from 'true' to 'false'.


**To Reproduce**
As an example from that PR:
``` typespec
@doc("Subscription trial availability")
model Trial {
@doc("Trial status")
@visibility("read")
status?: TrialStatus;
```

It does produce `readOnly`.
``` json
"status": {
"$ref": "#/definitions/TrialStatus",
"description": "Trial status",
"readOnly": true
},
```

But before it was not a `$ref`, it was inline:
```json
"status": {
"description": "Trial status",
"type": "string",
"enum": [
"TrialAvailable",
"TrialUsed",
"TrialDisabled"
],
"readOnly": true,
"x-ms-enum": {
"name": "TrialStatus",
"modelAsString": true
}
},
```

**Expected behavior**
It is not marked as a breaking change.

首先檢查 Azure/azure-rest-api-specs-pr#15631 中描述的比較，使用 Trial 模型和所參照的 TrialStatus enum 作為重現案例。追蹤 diff 在哪裡將先前的 inline enum schema 與新的 $ref schema 以及 readOnly 值進行比較。完成的標準是：此等效變更不再被回報為 readOnly breaking 變更。

由索引模型根據 Issue 內容生成。