Update tag

As part of improving kernel integration with the Hub: https://github.com/huggingface/huggingface.js/pull/1822 , we are using the `kernels` tag in place of `kernel` from now on. This is a small PR to update the tag.

README.md

@@ -1,7 +1,7 @@
 ---
 license: apache-2.0
 tags:
-- kernel
+- kernels
 ---
 
 ![Status](https://hubwebhook.dholtz.com/shield?repo=kernels-community/paged-attention)