Update README.md (#1573)

Update links to jest expect function.

packages/react-scripts/template/README.md

@@ -884,8 +884,8 @@ it('sums numbers', () => {
 });
 ```
 
-All `expect()` matchers supported by Jest are [extensively documented here](http://facebook.github.io/jest/docs/api.html#expect-value).<br>
-You can also use [`jest.fn()` and `expect(fn).toBeCalled()`](http://facebook.github.io/jest/docs/api.html#tobecalled) to create “spies” or mock functions.
+All `expect()` matchers supported by Jest are [extensively documented here](http://facebook.github.io/jest/docs/expect.html).<br>
+You can also use [`jest.fn()` and `expect(fn).toBeCalled()`](http://facebook.github.io/jest/docs/expect.html#tohavebeencalled) to create “spies” or mock functions.
 
 ### Testing Components
 
@@ -943,7 +943,7 @@ it('renders welcome message', () => {
 });
 ```
 
-All Jest matchers are [extensively documented here](http://facebook.github.io/jest/docs/api.html#expect-value).<br>
+All Jest matchers are [extensively documented here](http://facebook.github.io/jest/docs/expect.html).<br>
 Nevertheless you can use a third-party assertion library like [Chai](http://chaijs.com/) if you want to, as described below.
 
 Additionally, you might find [jest-enzyme](https://github.com/blainekasten/enzyme-matchers) helpful to simplify your tests with readable matchers. The above `contains` code can be written simpler with jest-enzyme.