Rename "Mac OS X" to "macOS" (elixir-lang#1248)

lucascaton · josevalim · commit 600842fc6771 · 2019-04-15T08:29:08.000+02:00
diff --git a/install.markdown b/install.markdown
@@ -19,7 +19,7 @@ The preferred option for installing Elixir. Choose your operating system and too
 
 If your distribution contains an old Elixir/Erlang version, see the sections below for installing Elixir/Erlang from version managers or from source.
 
-### Mac OS X
+### macOS
 
   * Homebrew
     * Update your homebrew to latest: `brew update`
