Fix typo.

releaser.conf

@@ -11,6 +11,6 @@ update_version {
 }
 update_version {
   path: "dulwich/__init__.py"
-  match: "^ __version__ = \((.*)\)$"
+  match: "^__version__ = \((.*)\)$"
   new_line: "__version__ = $TUPLED_VERSION"
 }