Bugfix/fix sonarcube findings (#6369)

* Fix sonarcube findings.
---------
Co-authored-by: Kim Kulling <kim.kulling@draeger.com>

code/PostProcessing/DropFaceNormalsProcess.h

@@ -52,7 +52,7 @@ namespace Assimp {
 // ---------------------------------------------------------------------------
 /** The DropFaceNormalsProcess computes face normals for all faces of all meshes
 */
-class ASSIMP_API_WINONLY DropFaceNormalsProcess : public BaseProcess {
+class ASSIMP_API_WINONLY DropFaceNormalsProcess final : public BaseProcess {
 public:
     DropFaceNormalsProcess() = default;
     ~DropFaceNormalsProcess() override = default;