Remove extra Vulkan submitCommandBuffer from deleteTestingOnlyBackendTexture

Change-Id: I6e2fd012d1c2af72a34be2d1971e210d7373fe21
Reviewed-on: https://skia-review.googlesource.com/120080
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
2 files changed