docs: update Krew installation guide's URL to official website

Author: wI2L

README.md

@@ -16,7 +16,7 @@ The plugin is compatible with Kubernetes servers starting from version 1.16, whi
 
 ### With [Krew](https://krew.sigs.k8s.io/)
 
-Follow these [instructions](https://github.com/kubernetes-sigs/krew#installation) to install `krew`. Then run the following commands:
+Follow these [instructions](https://krew.sigs.k8s.io/docs/user-guide/quickstart/) to install `krew`. Then run the following commands:
 
 ```shell
 $ kubectl krew install vpa-recommendation