remove reference to dev version of quarto (#69)

README.md

@@ -4,8 +4,6 @@ The book "Embrace Uncertainty: Fitting Mixed-Effects Models with Julia"
 
 This repository uses [Quarto](https://quarto.org) with the Julia code execution supplied by [QuartoNotebookRunner.jl](https://github.com/PumasAI/QuartoNotebookRunner.jl/), which requires Quarto 1.5+.
 
-As of early May 2024, Quarto 1.5 is only available as a preview release, which you'll need to [download from GitHub](https://github.com/quarto-dev/quarto-cli/releases). Under each release's "Assets", you can find platform-specific installers.
-
 ```sh
 ~/EmbraceUncertainty$ julia