Fix small typo in link_to_function doc

actionpack/lib/action_view/helpers/javascript_helper.rb

@@ -94,7 +94,7 @@ def button_to_function(name, function=nil, html_options={})
       # If +html_options+ has an <tt>:onclick</tt>, that one is put before +function+. Once all
       # the JavaScript is set, the helper appends "; return false;".
       #
-      # The +href+ attribute of the tag is set to "#" unles +html_options+ has one.
+      # The +href+ attribute of the tag is set to "#" unless +html_options+ has one.
       #
       #   link_to_function "Greeting", "alert('Hello world!')", :class => "nav_link"
       #   # => <a class="nav_link" href="#" onclick="alert('Hello world!'); return false;">Greeting</a>