fix lint issue - just a simple string

internal/server/dto.go

@@ -54,7 +54,7 @@ func decodeJSONBody(r *http.Request, dst interface{}) error {
 			msg := fmt.Sprintf("Request body contains badly-formed JSON (at position %d)", syntaxError.Offset)
 			return &malformedRequest{status: http.StatusBadRequest, message: msg}
 		case errors.Is(err, io.ErrUnexpectedEOF):
-			msg := fmt.Sprintf("Request body contains badly-formed JSON")
+			msg := "Request body contains badly-formed JSON"
 			return &malformedRequest{status: http.StatusBadRequest, message: msg}
 		case errors.As(err, &unmarshalTypeError):
 			msg := fmt.Sprintf("Request body contains an invalid value for the %q field (at position %d)", unmarshalTypeError.Field, unmarshalTypeError.Offset)