[regexp] implement case-insensitive unicode regexps.

src/regexp/regexp-ast.h

Index: src/regexp/regexp-ast.h
diff --git a/src/regexp/regexp-ast.h b/src/regexp/regexp-ast.h
index ed91a82d4934bf4e3d81cd342b40a1eecf6f024e..351ab00fa6750dbbcb70f5416b022caadfb129f3 100644
--- a/src/regexp/regexp-ast.h
+++ b/src/regexp/regexp-ast.h
@@ -293,7 +293,6 @@ class RegExpCharacterClass final : public RegExpTree {
   RegExpCharacterClass* AsCharacterClass() override;
   bool IsCharacterClass() override;
   bool IsTextElement() override { return true; }
-  bool NeedsDesugaringForUnicode(Zone* zone);
   int min_match() override { return 1; }
   int max_match() override { return 1; }
   void AppendToText(RegExpText* text, Zone* zone) override;