Fix LCD timer string length

Marlin/src/libs/duration_t.h

     if (with_days) {
       uint16_t d = this->day();
       sprintf_P(buffer, PSTR("%ud %02u:%02u"), d, h % 24, m);
-      return d >= 10 ? 8 : 7;
+      return d >= 10 ? 9 : 8;
     }
     else if (h < 100) {
       sprintf_P(buffer, PSTR("%02u:%02u"), h % 24, m);