remove unused function.

src/Workspaces/CSharp/Portable/LanguageServices/CSharpSyntaxFactsService.cs

@@ -84,11 +84,6 @@ public bool IsOperator(SyntaxToken token)
         public bool IsReservedKeyword(SyntaxToken token)
             => SyntaxFacts.IsReservedKeyword(token.Kind());
 
-        public bool IsReservedKeyword(string text)
-        {
-            return SyntaxFacts.GetKeywordKind(text) != SyntaxKind.None; // reserved keywords only
-        }
-
         public bool IsContextualKeyword(SyntaxToken token)
             => SyntaxFacts.IsContextualKeyword(token.Kind());