Remove a deprecated wstring ToLower function.

app/l10n_util.h

Index: app/l10n_util.h
diff --git a/app/l10n_util.h b/app/l10n_util.h
index 7f7b18aca910aaa2698fdc66fc5c222212c19a32..4ca6899bc5126ae834ccac6484f31b36791c084c 100644
--- a/app/l10n_util.h
+++ b/app/l10n_util.h
@@ -169,10 +169,6 @@ std::wstring GetStringF(int message_id, int64 a);
 std::wstring TruncateString(const std::wstring& string, size_t length);
 
 // Returns the lower case equivalent of string.
-#if defined(WCHAR_T_IS_UTF32)
-// Deprecated.  The string16 version should be used instead.
-std::wstring ToLower(const std::wstring& string);
-#endif  // defined(WCHAR_T_IS_UTF32)
 string16 ToLower(const string16& string);
 
 // Returns the upper case equivalent of string.