Remove shaderc cmake compiling

It is no longer needed as of https://skia.googlesource.com/skia/+/b7b4293524e0c1d4c1635c4710aceafaca47b313

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2060503002

Review-Url: https://codereview.chromium.org/2060503002
1 file changed