Vulkan: Optimize getIndexRange This function was unconditionally calling finishImpl(). This is changed to finishToSerial() to only wait until the serial that actually used the buffer. Bug: angleproject:3072 Change-Id: Ida89bb119b4ba6420f12404b911af0e3b4583a51 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1993407 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>