Stop trusting GetBestTranslation()

This started returning weird languages in some cases, like returning
"ja" when a user has their system set to Windows but also has a Japanese
language pack installed for e.g. a Japanese keyboard (even if it's not
enabled by default).

This will result in Aegisub always asking the user to pick a language on
first startup, but that's probably better anyway.

Author: arch1t3cht

src/aegisublocale.cpp

@@ -79,12 +79,6 @@ bool AegisubLocale::HasLanguage(std::string const& language) {
 }
 
 std::string AegisubLocale::PickLanguage() {
-	if (active_language.empty()) {
-		wxString os_ui_language = GetTranslations()->GetBestTranslation(AEGISUB_CATALOG);
-		if (!os_ui_language.empty())
-			return from_wx(os_ui_language);
-	}
-
 	wxArrayString langs = GetTranslations()->GetAvailableTranslations(AEGISUB_CATALOG);
 
 	// No translations available, so don't bother asking the user