Fix glCopyImageSubData() not work with multisample render buffer When target is "GL_RENDERBUFFER", and which is multisample, the function will not work. Bug: angleproject:382101118 Change-Id: I3d9c4a2550f9d66eeb73447328a03d4507cf2fa5 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6073359 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Yuxin Hu <yuxinhu@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>