RNTesterSnapshotTests: Fix testScrollViewExample failure

[hramos]

Help Wanted: Fix ScrollViewExample

test_objc on Circle CI is red due to a failing snapshot test, ScrollViewExample:

RNTesterSnapshotTests
  testScrollViewExample, failed: caught "NSInternalInconsistencyException", "Test failed"
  /Users/distiller/react-native/Libraries/RCTTest/RCTTestRunner.m:235
      RCTAssert(testModule.status != RCTTestStatusPending, @"Test didn't finish within %0.f seconds", kTestTimeoutSeconds);
      RCTAssert(testModule.status == RCTTestStatusPassed, @"Test failed");
    }

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

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.

[radko93]

@hramos I submitted a PR #22729

[hramos]

Fixed by #22729