bad underline

Martin Durant · Martin Durant · commit b19e38ef4b70 · 2021-06-17T10:07:06.000-04:00
diff --git a/docs/source/developer.rst b/docs/source/developer.rst
@@ -99,7 +99,7 @@ optional. Special considerations are required for async
 development, see :doc:`async`.
 
 Developing the library
-----------------------
+~~~~~~~~~~~~~~~~~~~~~~
 
 The following can be used to install ``fsspec`` in development mode
 
