update reno formatter invocation

Reno 2.1.0 had an API change. Update the release notes tool to use the
new API.

Change-Id: I23ce9a64ecd269e5b4ab9379a063067eb84d6460
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

releasetools/release_notes.py

@@ -355,7 +355,8 @@ def generate_release_notes(library, library_path,
         ldr = loader.Loader(conf=cfg)
         if end_revision in ldr.versions:
             rst_notes = formatter.format_report(
-                ldr,
+                loader=ldr,
+                config=cfg,
                 versions_to_include=[end_revision],
             )
             reno_notes = rst2txt.convert(rst_notes).decode('utf-8')