`stan_lmer` cannot be used through namespacing (`rstanarm::stan_lmer`) about rstanarm

[rempsyc]

This can be reproduced with R version 4.2.2 on Windows locally and on automated tests on GitHub actions machines.

R.Version()$version.string
#> [1] "R version 4.2.2 (2022-10-31 ucrt)"
R.Version()$platform
#> [1] "x86_64-w64-mingw32"
packageVersion("rstanarm")
#> [1] '2.21.3'

x <- rstanarm::stan_lmer(Sepal.Length ~ Petal.Length + (1 | Species),
                         data = iris, refresh = 0, iter = 1000, seed = 333)
#> Error in stan_glmer(formula = Sepal.Length ~ Petal.Length + (1 | Species), : could not find function "stan_glmer"

suppressPackageStartupMessages(library(rstanarm))

stan_glmer <<- rstanarm::stan_glmer
#> Error in eval(expr, envir, enclos): cannot change value of locked binding for 'stan_glmer'

^{Created on 2023-05-07 with reprex v2.0.2}