Exclude /lib/tasks/sample_data from CodeCov

We will almost certainly *never* invest the required amount of dev time to cover all this non-critical code with tests, so we may as well drop it from the report.

.simplecov

@@ -13,6 +13,7 @@ SimpleCov.start 'rails' do
   add_filter '/script'
   add_filter '/log'
   add_filter '/db'
+  add_filter '/lib/tasks/sample_data/'
 end
 
 require 'codecov'