Update How_to_count_tokens_with_tiktoken.ipynb

The PHP alternative is discontinued, its author is using the project to which this patch points to, which is also available in the PHP package manager.

See: CodeRevolutionPlugins/GPT-3-Encoder-PHP#1 (comment)

Author: DrDub

examples/How_to_count_tokens_with_tiktoken.ipynb

@@ -45,7 +45,7 @@
     "- JavaScript: [gpt-3-encoder](https://www.npmjs.com/package/gpt-3-encoder)\n",
     "- .NET / C#: [GPT Tokenizer](https://github.com/dluc/openai-tools)\n",
     "- Java: [gpt2-tokenizer-java](https://github.com/hyunwoongko/gpt2-tokenizer-java)\n",
-    "- PHP: [GPT-3-Encoder-PHP](https://github.com/CodeRevolutionPlugins/GPT-3-Encoder-PHP)\n",
+    "- PHP: [GPT3Tokenizer](https://github.com/Gioni06/GPT3Tokenizer)\n",
     "\n",
     "(OpenAI makes no endorsements or guarantees of third-party libraries.)\n",
     "\n",