combine_tbl_to_file: #| label: should be returned as it is, not as part of chunk header

[sda030]

Pretty sure that the Quarto people would frown upon this style now (even though still somewhat allowable):

```{r Import data for 07_Recruitment}
2+2
```

The current style (which was the original of the snippet above when using split_to_tbl) is

```{r}
#| label: "Import data for 07_Recruitment"
2+2
```

For extra safety I also think the quotation marks are in order.