Removed missing file from sksl.gni
Removed missing file from sksl.gni

sksl.gni still had a reference to a now-deleted file, which is
presumably the cause of the current build failures.

TBR=brianosman@google.com,johnstiles@google.com

Change-Id: I3a7d4514e338ca0810a21413e900248b1a2153e0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/439283
Reviewed-by: Ethan Nicholas <d2cfb8c2f603266f4dc3a6f09acbcc0089603b37@google.com>

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