Fix error with being unable to install php codesniffer on ubuntu 12.10

Recipe for PHP Codesniffer was specifying php_pear instead of
the internal chef_php_extra_pear, which was resulting in the following
error:

[2013-05-10T16:10:59+00:00] ERROR: php_pear[PHP_CodeSniffer]
(chef-php-extra::PHP_CodeSniffer line 22) has had an error
[2013-05-10T16:10:59+00:00] ERROR: php_pear[PHP_CodeSniffer]
(/tmp/vagrant-chef-1/chef-solo-1/cookbooks/chef-php-extra/recipes/PHP_CodeSniffer.rb:22:in
`from_file') had an error:
php_pear[PHP_CodeSniffer] (chef-php-extra::PHP_CodeSniffer line 22) had an
error: NameError: Cannot find a resource for converge_by on ubuntu version
12.10