RNTesterSnapshotTests: Fix testScrollViewExample flakiness

[hramos]

Help Wanted: Fix ScrollViewExample flakiness

As part of the RNTesterSnapshotTests, the RNTester ScrollViewExample is loaded and a screenshot is saved. The snapshot test is flaky as the Facebook thumbs images might not load before the screenshot is taken. This is therefore recorded as a failing snapshot test.

Comparison: blank snapshot on the left, and proper snapshot on the right.

The test is defined in JavaScript at RNTester/js/ScrollViewExample.js, and is invoked by RNTesterSnapshotTests.m in RNTester/RNTester.xcodeproj.

Potential solutions include delaying the recording of the snapshot long enough for images to have loaded, or simply replacing the images from ScrollViewExample with something else.

Steps to reproduce:

1. Run yarn at the repository root.
2. Open RNTester/RNTester.xcodeproj on Xcode 10.1.0.
3. Build RNTester.
4. Run tests (CMD+U) on an iPhone 6s simulator.

You can generate a new snapshot for comparison by editing RNTesterSnapshotTests.m and setting record mode to on.

[ericlewis]

I will take a look at this.

[ericlewis]

Updated in #23541, the solution was to remove the images and use a similar item style across all the examples.

[ericlewis]

@hramos we can close this now that #23541 was merged?