describe stringified response codes without referencing a specific format

In JSON, property keys are always strings; in YAML they may or not be
depending on the parser, but other formats may also be in use (TOML, TOON
etc). What matters is the resulting type(s) of the decoded data, not the
specific formatting used for the serialized form.

Author: karenetheridge

src/oas.md

@@ -2129,7 +2129,7 @@ call.
 
 | Field Pattern | Type | Description |
 | ---- | :----: | ---- |
-| <a name="responses-code"></a>[HTTP Status Code](#http-status-codes) | [Response Object](#response-object) \| [Reference Object](#reference-object) | Any [HTTP status code](#http-status-codes) can be used as the property name, but only one property per code, to describe the expected response for that HTTP status code. This field MUST be enclosed in quotation marks (for example, `"200"`) for compatibility between JSON and YAML. To define a range of response codes, this field MAY contain the uppercase wildcard character `X`. For example, `2XX` represents all response codes between `200` and `299`. Only the following range definitions are allowed: `1XX`, `2XX`, `3XX`, `4XX`, and `5XX`. If a response is defined using an explicit code, the explicit code definition takes precedence over the range definition for that code. |
+| <a name="responses-code"></a>[HTTP Status Code](#http-status-codes) | [Response Object](#response-object) \| [Reference Object](#reference-object) | Any [HTTP status code](#http-status-codes) can be used as the property name, but only one property per code, to describe the expected response for that HTTP status code. This field MUST be represented by a string (for example, `"200"`) for compatibility between JSON and YAML. To define a range of response codes, this field MAY contain the uppercase wildcard character `X`. For example, `2XX` represents all response codes between `200` and `299`. Only the following range definitions are allowed: `1XX`, `2XX`, `3XX`, `4XX`, and `5XX`. If a response is defined using an explicit code, the explicit code definition takes precedence over the range definition for that code. |
 
 This object MAY be extended with [Specification Extensions](#specification-extensions).