Update docs/core/compatibility/serialization/7.0/reflection-fallback.md

Co-authored-by: Genevieve Warren <24882762+gewarren@users.noreply.github.com>

Author: eiriktsarpalis

docs/core/compatibility/serialization/7.0/reflection-fallback.md

@@ -100,7 +100,7 @@ JsonSerializer.Serialize(new Poco2(), options); // Contract resolution falls bac
 options.GetConverter(typeof(Poco2)); // Returns the reflection-based converter.
 ```
 
-### Using the AppContext switch
+### Use an AppContext switch
 
 Starting in .NET 7 RC 2, you can re-enable reflection fallback globally using the provided AppContext compatibility switch. Add the following entry to your application's project file to re-enable reflection fallback for all source-generated contexts in your app. For more information on using AppContext switches, see the article on [.NET runtime configuration settings](../../../runtime-config/index.md).