Update toc.yml

Author: sally-baolian

articles/cognitive-services/Speech-Service/toc.yml

@@ -232,16 +232,16 @@ items:
       href: gaming-concepts.md
     - name: Language learning
       items:
-       - name: Overview
-         href: language-learning-overview.md
-       - name: Pronunciation Assessment with speech to text
-          items:
-            - name: Pronunciation Assessment in Speech Studio
-              href: pronunciation-assessment-tool.md
-              displayName: pronounce, learn language, assess pron
-            - name: How to use Pronunciation Assessment
-              href: how-to-pronunciation-assessment.md
-              displayName: pronounce, learn language, assess pron
+      - name: Overview
+        href: language-learning-overview.md
+      - name: Pronunciation Assessment with speech to text
+        items:
+        - name: Pronunciation Assessment in Speech Studio
+          href: pronunciation-assessment-tool.md
+          displayName: pronounce, learn language, assess pron
+        - name: How to use Pronunciation Assessment
+          href: how-to-pronunciation-assessment.md
+          displayName: pronounce, learn language, assess pron
     - name: Conversation transcription
       items:
         - name: Conversation Transcription overview