Remove some unused imports.

dulwich/fastexport.py

@@ -21,7 +21,6 @@
 """Fast export/import functionality."""
 
 from dulwich.objects import (
-    Tree,
     format_timezone,
     )
 

dulwich/web.py

@@ -32,8 +32,6 @@ from dulwich.protocol import (
     ReceivableProtocol,
     )
 from dulwich.server import (
-    ReceivePackHandler,
-    UploadPackHandler,
     DEFAULT_HANDLERS,
     )