[gn build] Port b0b2b2e

Author: llvmgnsyncbot

llvm/utils/gn/secondary/llvm/unittests/ADT/BUILD.gn

@@ -87,7 +87,6 @@ unittest("ADTTests") {
     "StringRefTest.cpp",
     "StringSetTest.cpp",
     "StringSwitchTest.cpp",
-    "StringViewExtrasTest.cpp",
     "TinyPtrVectorTest.cpp",
     "TwineTest.cpp",
     "TypeSwitchTest.cpp",