Fix doc typos

docs/guide/defining-documents.rst

@@ -178,7 +178,7 @@ either a single field name, or a list or tuple of field names::
     class User(Document):
         username = StringField(unique=True)
         first_name = StringField()
-        last_name = StringField(unique_with='last_name')
+        last_name = StringField(unique_with='first_name')
 
 Document collections
 ====================

docs/guide/querying.rst

@@ -172,7 +172,7 @@ custom manager methods as you like::
 
         @queryset_manager
         def live_posts(doc_cls, queryset):
-            return queryset.order_by('-date')
+            return queryset.filter(published=True)
 
     BlogPost(title='test1', published=False).save()
     BlogPost(title='test2', published=True).save()