Serializing context id causes many tests to fail capture replay test.
Remove it from the the GL context state's serialization.

Bug: angleproject:4817
Change-Id: Ide04f24c54d1f1fced532e49e85c0c2970816f5e
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2323645Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Commit-Queue: Manh Nguyen <nguyenmh@google.com>