Don't emit yaml suffixes in run and post-run lines

Change-Id: I16374d866faae3899c2cf8c09791774c968f3c66
diff --git a/zuul/cmd/migrate.py b/zuul/cmd/migrate.py
index 7338bdf..cb6e227 100644
--- a/zuul/cmd/migrate.py
+++ b/zuul/cmd/migrate.py
@@ -878,9 +878,9 @@
             output['parent'] = 'publish-openstack-artifacts'
         elif has_draft:
             output['success-url'] = 'html/'
-        output['run'] = os.path.join(self.job_path, 'run.yaml')
+        output['run'] = os.path.join(self.job_path, 'run')
         if has_post:
-            output['post-run'] = os.path.join(self.job_path, 'post.yaml')
+            output['post-run'] = os.path.join(self.job_path, 'post')
 
         if self.vars:
             output['vars'] = self.vars.copy()