docs: use proper term for {} characters

spec/asyncapi.md

@@ -351,7 +351,7 @@ An object representing a message broker, a server or any other kind of computer
 
 Field Name | Type | Description
 ---|:---:|---
-<a name="serverObjectUrl"></a>url | `string` | **REQUIRED**. A URL to the target host.  This URL supports Server Variables and MAY be relative, to indicate that the host location is relative to the location where the AsyncAPI document is being served. Variable substitutions will be made when a variable is named in `{`brackets`}`.
+<a name="serverObjectUrl"></a>url | `string` | **REQUIRED**. A URL to the target host.  This URL supports Server Variables and MAY be relative, to indicate that the host location is relative to the location where the AsyncAPI document is being served. Variable substitutions will be made when a variable is named in `{`braces`}`.
 <a name="serverObjectProtocol"></a>protocol | `string` | **REQUIRED**. The protocol this URL supports for connection. Supported protocol include, but are not limited to: `amqp`, `amqps`, `http`, `https`, `ibmmq`, `jms`, `kafka`, `kafka-secure`, `anypointmq`, `mqtt`, `secure-mqtt`, `solace`, `stomp`, `stomps`, `ws`, `wss`, `mercure`.
 <a name="serverObjectProtocolVersion"></a>protocolVersion | `string` | The version of the protocol used for connection. For instance: AMQP `0.9.1`, HTTP `2.0`, Kafka `1.0.0`, etc.
 <a name="serverObjectDescription"></a>description | `string` | An optional string describing the host designated by the URL. [CommonMark syntax](https://spec.commonmark.org/) MAY be used for rich text representation.