html-documents as exemple

tracim/views/core_api/schemas.py

     )
     label = marshmallow.fields.Str(example='Intervention Report 12')
     content_type = marshmallow.fields.Str(
-        example='html-content',
+        example='html-documents',
         validate=OneOf([content.slug for content in CONTENT_DEFAULT_TYPE]),
     )
     sub_content_types = marshmallow.fields.List(
 
 class HtmlDocumentContentSchema(ContentSchema):
     content_type = marshmallow.fields.Str(
-        example='html-content',
+        example='html-documents',
         validate=OneOf([content.slug for content in CONTENT_DEFAULT_TYPE]),
     )
     raw_content = marshmallow.fields.String('<p>Html page Content!</p>')
 
 class HtmlDocumentRevisionSchema(RevisionSchema):
     content_type = marshmallow.fields.Str(
-        example='html-content',
+        example='html-documents',
         validate=OneOf([content.slug for content in CONTENT_DEFAULT_TYPE]),
     )
     raw_content = marshmallow.fields.String('<p>Html page Content!</p>')