Wrong example about the https://github.com/Azure/openapi-diff/blob/master/docs/rules/1029.md

Hi team,

In the doc https://github.com/Azure/openapi-diff/blob/master/docs/rules/1029.md,
the Example is:
```
Example: readonly of property message **removed** in the new version.
```

However compared with the old specification, the new specification **added** "readonly" property

Open docs/rules/1029.md and compare the example with the rule's described change between the old and new OpenAPI specifications. Correct the example so it accurately says whether the readonly property was added or removed, then verify the rendered Markdown wording is clear.

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