Fix facebook#18279: Add 'addNetworkingHandler' to jest mock setup

Summary:
Fixes facebook#18279 by adding the correct methods to the jest mocks setup file.

Test by no longer including the workarounds in [issue comments](facebook#18279 (comment)). A [comment from hramos](facebook#18279 (comment)) mentioned improving the test coverage as well, but I wasn't certain how to achieve that.

[GENERAL] [BUGFIX] [BlobManager] - Fixed the jest mocks to avoid breaking tests
Closes facebook#18718

Differential Revision: D7542458

Pulled By: hramos

fbshipit-source-id: 77c9c7cae77971d62e878c4832b2e1d205131e8f

jest/setup.js

@@ -297,6 +297,7 @@ const mockNativeModules = {
   BlobModule: {
     BLOB_URI_SCHEME: 'content',
     BLOB_URI_HOST: null,
+    addNetworkingHandler: jest.fn(),
     enableBlobSupport: jest.fn(),
     disableBlobSupport: jest.fn(),
     createFromParts: jest.fn(),