Improve argument error messages in ext/sodium

Closes GH-5197

Author: kocsismate

Zend/zend.c

@@ -1528,12 +1528,7 @@ ZEND_API ZEND_COLD void zend_throw_error(zend_class_entry *exception_ce, const c
 	va_list va;
 	char *message = NULL;
 
-	if (exception_ce) {
-		if (!instanceof_function(exception_ce, zend_ce_error)) {
-			zend_error(E_NOTICE, "Error exceptions must be derived from Error");
-			exception_ce = zend_ce_error;
-		}
-	} else {
+	if (!exception_ce) {
 		exception_ce = zend_ce_error;
 	}