remove unused private function (#700)

Author: anonrig

include/ada/unicode.h

@@ -65,12 +65,6 @@ namespace ada::unicode {
 bool to_ascii(std::optional<std::string>& out, std::string_view plain,
               size_t first_percent);
 
-/**
- * @private
- * @see https://www.unicode.org/reports/tr46/#ToUnicode
- */
-std::string to_unicode(std::string_view input);
-
 /**
  * @private
  * Checks if the input has tab or newline characters.

src/unicode.cpp

@@ -479,8 +479,4 @@ std::string percent_encode(const std::string_view input,
   return out;
 }
 
-std::string to_unicode(std::string_view input) {
-  return ada::idna::to_unicode(input);
-}
-
 }  // namespace ada::unicode