Fix ShaderStorageBufferReadWriteOffset end2end test Test: ShaderStorageBufferTest31.ShaderStorageBufferReadWriteOffset. Align kBufferOffset to bufferAlignOffset correctly. Bug: angleproject:4471 Change-Id: I71084839a845138b32d58d8bd2cf6fed2633a9be Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2100047 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>