Delete unused class FakeScreenCapturerFactory.

Last use of the header file probably deleted in cl
https://codereview.webrtc.org/1903393004

BUG=None

Review-Url: https://codereview.webrtc.org/2353043003
Cr-Original-Commit-Position: refs/heads/master@{#14370}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 2a27b0a478f008ad17b29bb70e01bcec6c7d709d
3 files changed