Remove CURLUcode conversions for now since that requires curl 7.80

include/coeurl/errors.hpp

@@ -7,7 +7,7 @@
 
 namespace coeurl {
     const char* to_string(CURLcode c);
-    const char* to_string(CURLUcode c);
+    //const char* to_string(CURLUcode c);
     const char* to_string(CURLMcode c);
     const char* to_string(CURLSHcode c);
 };

lib/errors.cpp

@@ -4,9 +4,9 @@ const char* coeurl::to_string(CURLcode c) {
     return curl_easy_strerror(c);
 }
 
-const char* coeurl::to_string(CURLUcode c) {
-    return curl_url_strerror(c);
-}
+//const char* coeurl::to_string(CURLUcode c) {
+//    return curl_url_strerror(c);
+//}
 
 const char* coeurl::to_string(CURLMcode c) {
     return curl_multi_strerror(c);