Fixed minor typo on credits

railties/guides/source/credits.html.erb

@@ -44,7 +44,7 @@ Ruby on Rails Guides: Credits
 <% end %>
 
 <%= author('Mikel Lindsaar', 'raasdnil') do %>
-  Mikel Lindsaar has been working with Rails since 2006 and is the author of the Ruby <a hred="http://github.com/mikel/mail">Mail gem</a> and core contributor (he helped re-write Action Mailer's API). Mikel is the founder of <a href="http://rubyx.com/">RubyX</a>, has a <a href="http://lindsaar.net/">blog</a> and <a href="http://twitter.com/raasdnil">tweets</a>.
+  Mikel Lindsaar has been working with Rails since 2006 and is the author of the Ruby <a href="http://github.com/mikel/mail">Mail gem</a> and core contributor (he helped re-write Action Mailer's API). Mikel is the founder of <a href="http://rubyx.com/">RubyX</a>, has a <a href="http://lindsaar.net/">blog</a> and <a href="http://twitter.com/raasdnil">tweets</a>.
 <% end %>
 
 <%= author('Cássio Marques', 'cmarques') do %>