Fix docstring formatting in process_interactive_rebase

Fix documentation syntax error by using proper RST list formatting
for return value description.

dulwich/rebase.py

@@ -1033,9 +1033,10 @@ def process_interactive_rebase(
         editor_callback: Optional callback for reword operations
 
     Returns:
-        Tuple of (is_complete, pause_reason)
-        - is_complete: True if rebase is complete, False if paused
-        - pause_reason: Reason for pause (e.g., "edit", "conflict", "break") or None
+        Tuple of (is_complete, pause_reason):
+
+        * is_complete: True if rebase is complete, False if paused
+        * pause_reason: Reason for pause (e.g., "edit", "conflict", "break") or None
 
     Raises:
         RebaseError: If rebase fails