docs: use URL pointing to JSON Schema Draft 7 specs (#982)

spec/asyncapi.md

@@ -1702,7 +1702,7 @@ components:
 #### <a name="schemaObject"></a>Schema Object
 
 The Schema Object allows the definition of input and output data types.
-These types can be objects, but also primitives and arrays. This object is a superset of the [JSON Schema Specification Draft 07](https://json-schema.org/). The empty schema (which allows any instance to validate) MAY be represented by the `boolean` value `true` and a schema which allows no instance to validate MAY be represented by the `boolean` value `false`.
+These types can be objects, but also primitives and arrays. This object is a superset of the [JSON Schema Specification Draft 07](https://json-schema.org/specification-links.html#draft-7). The empty schema (which allows any instance to validate) MAY be represented by the `boolean` value `true` and a schema which allows no instance to validate MAY be represented by the `boolean` value `false`.
 
 Further information about the properties can be found in [JSON Schema Core](https://tools.ietf.org/html/draft-handrews-json-schema-01) and [JSON Schema Validation](https://tools.ietf.org/html/draft-handrews-json-schema-validation-01).
 Unless stated otherwise, the property definitions follow the JSON Schema specification as referenced here.