Remove the Vulkan index-map variant

RNE's semantic segmenter accepts only the per-class score map, so this export
could not be loaded by the library.

vulkan/lraspp_mobilenet_v3_large_vulkan_fp16_index.pte

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:64c363ce0b11c791e2ed0bdbc2ac8d4251ae5f2d5f555bd4ab236c638164a97c
-size 6509316