Removes redundant std::endl.

Bug: angleproject:5751
Change-Id: Ia7e0d7c4550c2565a3787d433ea245db95856b30
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2773291
Commit-Queue: Lubosz Sarnecki <lubosz.sarnecki@collabora.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>