@uppy/core: remove `state` getter from types (#4477)

The `state` getter was removed a while back, and we forgot to fix the types.

packages/@uppy/core/types/index.d.ts

@@ -284,8 +284,6 @@ export class Uppy {
 
   getState<TMeta extends IndexedObject<any> = Record<string, unknown>>(): State<TMeta>
 
-  readonly state: State
-
   setFileState(fileID: string, state: Record<string, unknown>): void
 
   resetProgress(): void