[typings] Update typings to popover changes (#7937)

src/Menu/Menu.d.ts

@@ -1,6 +1,6 @@
 import * as React from 'react';
 import { StyledComponent } from '..';
-import { PopoverProps } from '../internal/Popover';
+import { PopoverProps } from '../Popover';
 import { TransitionHandlers } from '../internal/Transition';
 import { MenuListProps } from './MenuList';
 

src/Popover/Popover.d.ts

@@ -1,7 +1,7 @@
 import * as React from 'react';
 import { StyledComponent } from '..';
 import { PaperProps } from '../Paper';
-import { TransitionHandlers } from './Transition';
+import { TransitionHandlers } from '../internal/Transition';
 
 export type Origin = {
   horizontal: 'left' | 'center' | 'right' | number;

src/Popover/index.d.ts

@@ -0,0 +1,2 @@
+export { default } from './Popover';
+export * from './Popover';