Now that 3.0 support is passing dEQP, always return that as the
context version to use (unless app asks for 1.0).

Test: angle_end2end --gtest_filter=EGLBackwardsCompatibleContextTest.BackwardsCompatibleEnabledES3/*
Bug: angleproject:3750
Change-Id: I0402ac015acfc22e84a985fe75346999bcc47188
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1906202Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Tobin Ehlis <tobine@google.com>
Commit-Queue: Courtney Goeltzenleuchter <courtneygo@google.com>