Merge pull request #22429 from Huang-Wei/postfilter-doc

Document the changes of scheduler PostFilter extension point

content/en/docs/reference/scheduling/config.md

@@ -158,6 +158,8 @@ extension points:
   Extension points: `QueueSort`.
 - `DefaultBinder`: Provides the default binding mechanism.
   Extension points: `Bind`.
+- `DefaultPreemption`: Provides the default preemption mechanism.
+  Extension points: `PostFilter`.
   
 You can also enable the following plugins, through the component config APIs,
 that are not enabled by default:
@@ -199,7 +201,7 @@ profiles:
   - schedulerName: default-scheduler
   - schedulerName: no-scoring-scheduler
     plugins:
-      prescore:
+      preScore:
         disabled:
         - name: '*'
       score:
@@ -230,22 +232,6 @@ the same configuration parameters (if applicable). This is because the scheduler
 only has one pending pods queue.
 {{< /note >}}
 
-## Upgrading from `v1alpha2` to `v1beta1` {#beta-changes}
-
-When migrating from `kubescheduler.config.k8s.io/v1alpha2` to `kubescheduler.config.k8s.io/v1beta1`,
-beware of the following changes, if applicable:
-
-- `.bindTimeoutSeconds` was moved as part of plugin args for `VolumeBinding`,
-  which can be configured separately per [profile](#profiles).
-- `.extenders` are updated to satisfy API standards. In particular:
-  - `.extenders` decoding is case sensitive. All fields are affected.
-  - `.extenders[*].httpTimeout` is of type `metav1.Duration`.
-  - `.extenders[*].enableHttps` is renamed to `.extenders[*].enableHTTPS`.
-- `RequestedToCapacityRatio` args decoding is case sensitive. All fields are affected.
-- `DefaultPodTopologySpread` [plugin](#scheduling-plugins) is renamed to `SelectorSpread`.
-- `Unreserve` extension point is removed from Profile definition. All `Reserve`
-  plugins implement an `Unreserve` call.
-
 ## {{% heading "whatsnext" %}}
 
 * Read the [kube-scheduler reference](https://kubernetes.io/docs/reference/command-line-tools-reference/kube-scheduler/)