mention when c26865 was added to VS

Author: carsonRadtke

docs/code-quality/c26865.md

@@ -10,6 +10,8 @@ ms.assetid: 2fbe9dc5-fa43-47b9-97a7-3f8215da1d40
 
 > Memory allocated with '\<allocation-function\>' is being deallocated with '\<wrong-deallocation-function\>'. Use '\<correct-deallocation-function\>' instead.
 
+This rule was added in Visual Studio 2026 18.0.
+
 ## Remarks
 
 This warning indicates that the memory was allocated with one family of allocation functions, but was freed with a deallocation function from a different family. This usage results in undefined behavior according to C/C++ and the Microsoft MSVC implementation.