[Grid] Remove unnecessary type exports

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

@@ -832,6 +832,24 @@ As the core components use emotion as a styled engine, the props used by emotion
   });
   ```
 
+- The auxiliary types `GridDirection`, `GridSpacing`, `GridWrap` and `GridSize` are not exported anymore. Instead, get them from `GridProps`.
+
+  ```diff
+  -import { GridDirection, GridSpacing, GridWrap, GridSize } from '@material-ui/core/Grid';
+  +import { GridProps } from '@material-ui/core/Grid';
+
+  interface Props {
+  - direction: GridDirection;
+  - spacing: GridSpacing;
+  - wrap: GridWrap;
+  - size: GridSize;
+  + direction: GridProps['direction'];
+  + spacing: GridProps['spacing'];
+  + wrap: GridProps['wrap'];
+  + size: GridProps['xs'] & (string | number);
+  }
+  ```
+
 ### GridList
 
 - Rename the `GridList` components to `ImageList` to align with the current Material Design naming.

packages/material-ui/src/Grid/Grid.d.ts

@@ -3,13 +3,13 @@ import { SxProps, SystemProps } from '@material-ui/system';
 import { Theme } from '../styles';
 import { OverridableComponent, OverrideProps } from '../OverridableComponent';
 
-export type GridDirection = 'row' | 'row-reverse' | 'column' | 'column-reverse';
+type GridDirection = 'row' | 'row-reverse' | 'column' | 'column-reverse';
 
-export type GridSpacing = number | string;
+type GridSpacing = number | string;
 
-export type GridWrap = 'nowrap' | 'wrap' | 'wrap-reverse';
+type GridWrap = 'nowrap' | 'wrap' | 'wrap-reverse';
 
-export type GridSize = 'auto' | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12;
+type GridSize = 'auto' | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12;
 
 export type GridClassKey = keyof NonNullable<GridTypeMap['props']['classes']>;