brew.sh: Remove useless use of sudo

Thanks to @jonnybarnes for spotting this.

Closes mathiasbynens#647.

brew.sh

@@ -2,12 +2,6 @@
 
 # Install command-line tools using Homebrew.
 
-# Ask for the administrator password upfront.
-sudo -v
-
-# Keep-alive: update existing `sudo` time stamp until the script has finished.
-while true; do sudo -n true; sleep 60; kill -0 "$$" || exit; done 2>/dev/null &
-
 # Make sure we’re using the latest Homebrew.
 brew update
 
@@ -17,7 +11,7 @@ brew upgrade --all
 # Install GNU core utilities (those that come with OS X are outdated).
 # Don’t forget to add `$(brew --prefix coreutils)/libexec/gnubin` to `$PATH`.
 brew install coreutils
-sudo ln -s /usr/local/bin/gsha256sum /usr/local/bin/sha256sum
+ln -s /usr/local/bin/gsha256sum /usr/local/bin/sha256sum
 
 # Install some other useful utilities like `sponge`.
 brew install moreutils