Only one "is" is necessary (review feedback)

Co-authored-by: Mike Kistler <[email protected]>

Author: handrews

versions/3.0.4.md

@@ -2752,7 +2752,7 @@ However, it is RECOMMENDED to search all named schemas in the Components Object
 The behavior of any configuration of `oneOf`, `anyOf`, `allOf` and `discriminator` that is not described above is undefined.
 
 ##### Options for Mapping Values to Schemas
-The value of the property named in `propertyName` is is used as the name of the associated schema under the [Components Object](#componentsObject), _unless_ a `mapping` is present for that value.
+The value of the property named in `propertyName` is used as the name of the associated schema under the [Components Object](#componentsObject), _unless_ a `mapping` is present for that value.
 The `mapping` entry maps a specific property value to either a different schema component name, or to a schema identified by a URI.
 When using implicit or explicit schema component names, inline `oneOf` or `anyOf` subschemas are not considered.
 The behavior of a `mapping` value that is both a valid schema name and a valid relative URI reference is implementation-defined, but it is RECOMMENDED that it be treated as a schema name.