Fix links for k/design-proposals-archive

The contributors/design-proposals in k/community was removed. It's only
available in k/design-proposals-archive repo now.

This commit also changes https://github.com/kubernetes/repo/blob/master/file.md
to https://git.k8s.io/repo/file.md for better consistency.

content/en/docs/concepts/extend-kubernetes/_index.md

@@ -160,7 +160,7 @@ After a request is authorized, if it is a write operation, it also goes through
 
 ### Storage Plugins
 
-[Flex Volumes](https://github.com/kubernetes/community/blob/master/contributors/design-proposals/storage/flexvolume-deployment.md
+[Flex Volumes](https://git.k8s.io/design-proposals-archive/storage/flexvolume-deployment.md
 ) allow users to mount volume types without built-in support by having the
 Kubelet call a Binary Plugin to mount the volume.
 
@@ -191,7 +191,7 @@ This is a significant undertaking, and almost all Kubernetes users find they
 do not need to modify the scheduler.
 
 The scheduler also supports a
-[webhook](https://github.com/kubernetes/community/blob/master/contributors/design-proposals/scheduling/scheduler_extender.md)
+[webhook](https://git.k8s.io/design-proposals-archive/scheduling/scheduler_extender.md)
 that permits a webhook backend (scheduler extension) to filter and prioritize
 the nodes chosen for a pod.
 

content/en/docs/concepts/extend-kubernetes/compute-storage-net/device-plugins.md

@@ -8,7 +8,7 @@ weight: 20
 <!-- overview -->
 {{< feature-state for_k8s_version="v1.10" state="beta" >}}
 
-Kubernetes provides a [device plugin framework](https://github.com/kubernetes/community/blob/master/contributors/design-proposals/resource-management/device-plugin.md)
+Kubernetes provides a [device plugin framework](https://git.k8s.io/design-proposals-archive/resource-management/device-plugin.md)
 that you can use to advertise system hardware resources to the
 {{< glossary_tooltip term_id="kubelet" >}}.