[Bug]: Can't install dependency Rcpp for min_cohort, keeps looking for R >= 4.6

### What happened?

```
Error : ! Could not solve package dependencies:
* deps::/tmp/RtmpY1Jick/filebb4d5687ff: Can't install dependency flextable (>= 0.9.10)
* flextable: Can't install dependency gdtools (>= 0.4.0)
* gdtools: Can't install dependency Rcpp (>= 0.12.12)
* Rcpp: Needs R >= 4.6
```

https://github.com/insightsengineering/rtables.officer/actions/runs/20610588459/job/59194224285

### Which version(s) of R were you using?

_No response_

### Relevant log output

```R

```

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