Remove 'sudo' from the npm installation instructions

Using 'sudo' should not be required to install npm, and isn't if the
user has used the default Homebrew installation process.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Library/Homebrew/blacklist.rb

@@ -42,7 +42,7 @@ def blacklisted? name
       http://npmjs.org/
 
     To do it in one line, use this command:
-      curl http://npmjs.org/install.sh | sudo sh
+      curl http://npmjs.org/install.sh | sh
     EOS
   end
 end