Update PACKAGE.md

Author: tarekgh

src/Microsoft.ML.Tokenizers/PACKAGE.md

@@ -15,7 +15,7 @@ Microsoft.ML.Tokenizers supports various the implmentation of the tokenization u
 using Microsoft.ML.Tokenizers;
 
 // initialize the tokenizer for `gpt-4` model, downloading data files
-Tokenizer tokenizer = await Tiktoken.CreateByModelNameAsync("gpt-4");
+Tokenizer tokenizer = await Tokenizer.CreateTiktokenForModelAsync("gpt-4");
 
 string source = "Text tokenization is the process of splitting a string into a list of tokens.";
 
@@ -58,4 +58,4 @@ The main types provided by this library are:
 
 ## Feedback & Contributing
 
-Microsoft.ML.Tokenizers is released as open source under the [MIT license](https://licenses.nuget.org/MIT). Bug reports and contributions are welcome at [the GitHub repository](https://github.com/dotnet/machinelearning).
+Microsoft.ML.Tokenizers is released as open source under the [MIT license](https://licenses.nuget.org/MIT). Bug reports and contributions are welcome at [the GitHub repository](https://github.com/dotnet/machinelearning).