Fixed #7838 -- Corrected an invalid class name the 'classes' usage in the…

Fixed #7838 -- Corrected an invalid class name the 'classes' usage in the tutorial. Thanks kratorius for catching this.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@7984 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/tutorial02.txt

@@ -192,7 +192,7 @@ aren't commonly used::
         class PollAdmin(admin.ModelAdmin):
             fieldsets = [
                 (None,               {'fields': ['question']}),
-                ('Date information', {'fields': ['pub_date'], 'classes': ['pub_date']}),
+                ('Date information', {'fields': ['pub_date'], 'classes': ['collapse']}),
             ]
 
 .. image:: http://media.djangoproject.com/img/doc/tutorial-trunk/admin09.png
@@ -242,7 +242,7 @@ registration code to read::
     class PollAdmin(admin.ModelAdmin):
         fieldsets = [
             (None,               {'fields': ['question']}),
-            ('Date information', {'fields': ['pub_date'], 'classes': ['pub_date']}),
+            ('Date information', {'fields': ['pub_date'], 'classes': ['collapse']}),
         ]
         inlines = [ChoiceInline]