MDX: fix JSX format (#9267)

changelog_unreleased/mdx/pr-9267.md

@@ -0,0 +1,35 @@
+#### Fix JSX format (#9267 by @fisker)
+
+<!-- prettier-ignore -->
+```markdown
+<!-- Input -->
+# title
+
+<Jsx>
+
+text
+
+</Jsx>
+
+<!-- Prettier stable -->
+# title
+
+<Jsx>
+
+
+text
+
+</Jsx>
+
+
+(Extra empty lines added after `<Jsx>` and `</Jsx>`)
+
+<!-- Prettier master -->
+# title
+
+<Jsx>
+
+text
+
+</Jsx>
+```