Replace extra substr() call (#3430)

This was possible after a $newkey assignment was introduced in bd9ef30

Author: jmikola

src/Query/Builder.php

@@ -1896,7 +1896,7 @@ private function aliasIdForQuery(array $values, bool $root = true): array
                     throw new InvalidArgumentException(sprintf('Cannot have both "%s" and "%s" fields.', $key, $newkey));
                 }
 
-                $values[substr($key, 0, -3) . '._id'] = $value;
+                $values[$newkey] = $value;
                 unset($values[$key]);
             }
         }