Do not explicitly namespace epiparameter

To avoid loading it (and its dependencies) before renv::use() even got the chance to run, thus creating version conflicts between already loaded packages and requested versions.
It seems for some reason that explicitly namespaced packages are automatically loaded in Rmd documents

inst/rmarkdown/templates/transmissibility/skeleton/skeleton.Rmd

@@ -391,7 +391,7 @@ discretized Gamma.
 ## Results
 
 ```{r, eval = params$use_epiparameter_database}
-si_epidist <- epiparameter::epidist_db(
+si_epidist <- epidist_db(
   disease =  params$disease_name,
   epi_dist =  "serial_interval",
   single_epidist = TRUE,
@@ -418,7 +418,7 @@ si_epidist <- epidist(
 ```
 
 ```{r}
-si <- epiparameter::discretise(si_epidist)
+si <- discretise(si_epidist)
 si_x <- seq(1L, to = quantile(si, 0.999), by = 1L)
 ```