Vulkan: Fix FS array output location assignment Test: angle_end2end_test --gtest_filter=GLSLTest_ES3.FragmentShaderOutputArray/ES3_Vulkan Bug: angleproject:3707 Change-Id: I6519a76aa58ad80ada0e2ad90a2a70d93f831ce5 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1704779 Commit-Queue: Courtney Goeltzenleuchter <courtneygo@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>