Update docs/code-quality/ca2009.md

Co-Authored-By: Mike Jones <[email protected]>

Author: mavasani

docs/code-quality/ca2009.md

@@ -54,7 +54,7 @@ These extension methods are designed to convert a mutable collection to an immut
 
 ## How to fix violations
 
-To fix violations, remove the redundant `ToImmutable` call on an immutable collection. For example, the following two code snippets show a violation of the rule and how to fix it:
+To fix violations, remove the redundant `ToImmutable` call on an immutable collection. For example, the following two code snippets show a violation of the rule and how to fix them:
 
 ```csharp
 using System;