fix mdx -> tsx

Author: rtso

apps/nextra/pages/en/build/indexer/indexer-sdk/documentation/steps/_meta.mdx

@@ -0,0 +1,8 @@
+export default {
+  "transaction-stream": {
+    title: "Transaction Stream Step",
+  },
+  "parsing-txns": {
+    title: "Parsing Transactions",
+  },
+};