select_ has been depreciated - R dyplot.prophet

The select_ syntax has been deprecaited in dplyr for a while now. Line 473 on plot.R should be updated from
```{r}
dfTS <- xts::xts(df %>% dplyr::select_(.dots=colsToKeep), order.by = df$ds)
```
to
```{r}
dfTS <- xts::xts(df %>% dplyr::select(.cols = all_of(colsToKeep)), order.by = df$ds)
```