addinitional -> additional typo fix

Author: Lucie Tvrznikova

clang/lib/StaticAnalyzer/Checkers/UninitializedObject/UninitializedObject.h

@@ -79,7 +79,7 @@ struct UninitObjCheckerOptions {
 };
 
 /// A lightweight polymorphic wrapper around FieldRegion *. We'll use this
-/// interface to store addinitional information about fields. As described
+/// interface to store additional information about fields. As described
 /// later, a list of these objects (i.e. "fieldchain") will be constructed and
 /// used for printing note messages should an uninitialized value be found.
 class FieldNode {