C#: delete override where the parent predicate no longer existed

Author: erik-krogh

csharp/ql/src/experimental/ir/implementation/raw/internal/desugar/internal/TranslatedCompilerGeneratedElement.qll

@@ -20,7 +20,4 @@ abstract class TranslatedCompilerGeneratedElement extends TranslatedElement,
   final override Callable getFunction() { result = generatedBy.getEnclosingCallable() }
 
   final override Language::AST getAst() { result = generatedBy }
-
-  /** DEPRECATED: Alias for getAst */
-  deprecated override Language::AST getAST() { result = this.getAst() }
 }