Remove DEPS on shaderc and glslang

These were used by Dawn at some point but are no longer needed since
they are only used by Dawn's tests that aren't discovered by Skia's GN
build.

Bug: dawn:706
Change-Id: Icb75856955c16f659203ebf20462db59f4165873
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/381236
Auto-Submit: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Eric Boren <borenet@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
6 files changed