Fix TOC name (#27806)

* Fix TOC name

* Fix in other spot too

Author: gewarren

docs/core/compatibility/toc.yml

@@ -25,7 +25,7 @@ items:
         href: 7.0.md
       - name: Core .NET libraries
         items:
-        - name: Default serialization format for TimeSpan
+        - name: Validate CompressionLevel for BrotliStream
           href: core-libraries/7.0/compressionlevel-validation.md
     - name: .NET 6
       items:
@@ -637,7 +637,7 @@ items:
       items:
       - name: .NET 7
         items:
-        - name: Default serialization format for TimeSpan
+        - name: Validate CompressionLevel for BrotliStream
           href: core-libraries/7.0/compressionlevel-validation.md
       - name: .NET 6
         items: