removed invalid boolean types from metadata.rb in dependencies cookbook

Per http://docs.opscode.com/essentials_cookbook_metadata.html, the ````type```` parameter of an ````attribute```` defined in ````metadata.rb```` can only have values ````'string'```` or ````'array'````.  

However, the ````type```` parameter in the dependencies cookbook is set to ````'boolean'````.  Since the ````type```` parameter is not required, this PR just removes these invalid ````type```` uses from this cookbook's metadata.

Note that this change is also in #6's larger attempt to fix up metadata.  Also, https://github.com/scalarium/cookbooks/pull/15 tries to fix this same problem with the dependencies cookbook but they go further to say that the ````type```` should be ````'string'```` and they also change the use of ````true```` and ````false```` in the cookbook to ````'true'```` and ````'false'````.  I imagine the current use of booleans in the cookbook code is working, so I didn't make that change.

Reference: #31