Remove redundant calls to simplify_vector.
Remove redundant calls to simplify_vector.

Originally, `simplify_vector` took a template parameter for the value
type, and so we needed to distinguish between SKSL_INT and float
vectors when simplifying them. This distinction was eliminated a while
ago (at http://review.skia.org/447836 ) so we can now handle all numeric
vector types the same way.

Change-Id: I55b1f4bf64c766148e8e25a23634e4b13c1c8f1e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/497699
Auto-Submit: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>
Reviewed-by: Brian Osman <794c0b5534edf5601d88e1d41975d0262da12894@google.com>
Commit-Queue: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>

google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia