rename cuda mode -> gpu mode (#925)

Author: msaroufim

README.md

@@ -1,6 +1,6 @@
 # torchao: PyTorch Architecture Optimization
 
-[![](https://dcbadge.vercel.app/api/server/cudamode?style=flat)](https://discord.gg/cudamode)
+[![](https://dcbadge.vercel.app/api/server/gpumode?style=flat)](https://discord.gg/gpumode)
 
 [Introduction](#introduction) | [Inference](#inference) | [Training](#training)  | [Composability](#composability) | [Custom Kernels](#custom-kernels) | [Alpha Features](#alpha-features) | [Installation](#installation) | [Integrations](#integrations) | [Videos](#videos) | [License](#license)