brew.sh: Remove dependency on homebrew/versions

brew.sh

@@ -20,9 +20,8 @@ brew install findutils
 brew install gnu-sed --with-default-names
 # Install Bash 4.
 # Note: don’t forget to add `/usr/local/bin/bash` to `/etc/shells` before
-# running `chsh`. To do so, run `sudo chsh -s /usr/local/bin/bash`.
+# running `chsh`.
 brew install bash
-brew tap homebrew/versions
 brew install bash-completion2
 
 # Switch to using brew-installed bash as default shell