docs: simplify installation section

README.md

@@ -120,19 +120,12 @@ shinyApp(ui, server)
 
 <h2 id="install">Installation</h2>
 
-To install the stable CRAN version:
+To install the latest version from CRAN:
 
 ```
 install.packages("shinyalert")
 ```
 
-To install the latest development version from GitHub:
-
-```
-install.packages("remotes")
-remotes::install_github("daattali/shinyalert")
-```
-
 <h2 id="input-modals">Simple input modals</h2>
 
 Usually the purpose of a modal is simply informative, to show some information to the user. However, the modal can also be used to retrieve an input from the user by setting the `type = "input"` parameter.