[docs] Only include v4 -> v5 instructions

docs/src/pages/guides/migration-v4/migration-v4.md

@@ -852,28 +852,6 @@ As the core components use emotion as a styled engine, the props used by emotion
   +<Icon>icon-name</Icon>
   ```
 
-### LoadingButton
-
-- Rename `pending` prop to `loading`.
-- Rename `pendingIndicator` prop to `loadingIndicator`.
-- Rename `pendingPosition` prop to `loadingPosition`.
-
-  ```diff
-  -<LoadingButton pending pendingIndicator="Pending..." pendingPosition="end" />
-  +<LoadingButton loading loadingIndicator="Pending..." loadingPosition="end" />
-  ```
-
-- The following keys of the `classes` prop were also renamed:
-
-  1. `pending` to `loading`
-  1. `pendingIndicator` to `loadingIndicator`
-  1. `pendingIndicatorCenter` to `loadingIndicatorCenter`
-  1. `pendingIndicatorStart` to `loadingIndicatorStart`
-  1. `pendingIndicatorEnd` to `loadingIndicatorEnd`
-  1. `endIconPendingEnd` to `endIconLoadingEnd`
-  1. `startIconPendingStart` to `startIconLoadingStart`
-  1. `labelPendingCenter` to `labelLoadingCenter`
-
 ### Menu
 
 - The onE\* transition props were removed. Use TransitionProps instead.