Add a note about how we can get rid of a thing soon.

Author: nedbat

django_coverage_plugin/plugin.py

@@ -226,6 +226,7 @@ def statements(self):
 
         return source_lines
 
+    # Note: this function won't be needed after coverage.py 4.0a5.
     def no_branch_lines(self):
         return set()