Update contribute-code.md

the workflow's link is wrong,miss .md.
diff --git a/docs-site/docs/contribute-code.md b/docs-site/docs/contribute-code.md
index 4b55744..6f7d50b 100644
--- a/docs-site/docs/contribute-code.md
+++ b/docs-site/docs/contribute-code.md
@@ -122,4 +122,4 @@
 
 ## Workflow
 
-Please refer to the [git workflow page](./git-workflow).
+Please refer to the [git workflow page](./git-workflow.md).