Flow fixes for test renderer

Author: kassens

packages/react-test-renderer/src/ReactFiberConfigTestHost.js

@@ -268,7 +268,7 @@ export const warnsIfNotActing = true;
 export const scheduleTimeout = setTimeout;
 export const cancelTimeout = clearTimeout;
 
-export const noTimeout = -1;
+export const noTimeout: -1 = -1;
 
 // -------------------
 //     Mutation

packages/react-test-renderer/src/ReactTestRenderer.js

@@ -61,6 +61,7 @@ import {
 } from 'shared/ReactFeatureFlags';
 
 import noop from 'shared/noop';
+import type {WorkTag} from 'react-reconciler/src/ReactWorkTags';
 
 const defaultOnDefaultTransitionIndicator: () => void | (() => void) = noop;
 
@@ -244,7 +245,7 @@ function toTree(node: null | Fiber): $FlowFixMe {
   }
 }
 
-const validWrapperTypes = new Set([
+const validWrapperTypes: Set<WorkTag> = new Set([
   FunctionComponent,
   ClassComponent,
   HostComponent,