Modify the typo in order to deploy the correct configuration file.

In order to deploy the configuration file for processing `aptitude` log
file, fix the following typo:

```
-cookbook_file "/etc/td-agent/conf.d/processor_dstat.conf" do
-  source "processor_dstat.conf"
+cookbook_file "/etc/td-agent/conf.d/processor_aptitude.conf" do
+  source "processor_aptitude.conf"

   owner "root"
  group "root"
```