[gardening] Dead File Elimination

Author: milseman

stdlib/public/core/CMakeLists.txt

@@ -166,7 +166,6 @@ set(SWIFTLIB_ESSENTIAL
   StringUTF16View.swift
   StringUTF8View.swift
   StringUTF8Validation.swift
-  StringVariant.swift
   Substring.swift
   SwiftNativeNSArray.swift
   ThreadLocalStorage.swift

stdlib/public/core/GroupInfo.json

@@ -40,7 +40,6 @@
     "StringUTF8View.swift",
     "StringUTF8Validation.swift",
     "StringUnicodeScalarView.swift",
-    "StringVariant.swift",
     "Substring.swift",
     "Unicode.swift",
     "UnicodeEncoding.swift",