docs(article): fix type in 'param_optim'

page_2.1_param_optim.Rmd

@@ -224,7 +224,7 @@ Here we use the following R implementation of an efficient strategy:
 
 Motivated by using the rainfall-runoff model for low flow simulation, we explore the trade-offs between the KGE values obtained without any data transformation and with the inverse transformation.
 
-First, the OptimGR4J function previously used is modified to return two values.
+First, the `OptimGR4J()` function previously used is modified to return two values.
 
 ```{r, warning=FALSE, results='hide', eval=FALSE}
 InputsCrit_inv <- InputsCrit