Remove redundant words.

Author: Renke Christian von Seggern

src/main/antora/modules/ROOT/pages/mongodb/mapping/mapping.adoc

@@ -70,7 +70,7 @@ No further conversion happens unless `@MongoId` declares a desired field type.
 If no value is provided for the `id` field, a new `ObjectId` will be created and converted to the properties type.
 * If a field is annotated with `@MongoId(FieldType.…)` in the Java class it will be attempted to convert the value to the declared `FieldType`.
 If no value is provided for the `id` field, a new `ObjectId` will be created and converted to the declared type.
-* If a field named `id` id field is not declared as a String, BigInteger, or ObjectID in the Java class then you should assign it a value in your application so it can be stored 'as-is' in the document's _id field.
+* If a field named `id` is not declared as a String, BigInteger, or ObjectID in the Java class then you should assign it a value in your application so it can be stored 'as-is' in the document's _id field.
 * If no field named `id` is present in the Java class then an implicit `_id` file will be generated by the driver but not mapped to a property or field of the Java class.
 
 When querying and updating `MongoTemplate` will use the converter to handle conversions of the `Query` and `Update` objects that correspond to the above rules for saving documents so field names and types used in your queries will be able to match what is in your domain classes.