EGL_EXT_buffer_age was previously disabled for SwiftShader Vulkan
because of an Android test timing out on Cuttlefish when the buffer
age is queried. aosp/1672445 addresses the root cause of the timeout,
so EGL_EXT_buffer_age can be supported again.

Bug: b/182521420
Bug: angleproject:3529
Change-Id: I5949f721316855d9138eb9f657a6df4e7b49ed71
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2821750Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Nicolas Capens <nicolascapens@google.com>