Enable facterdb string keys

In the process of reviewing an unrelated facter issue, I noticed that
this (setting `facterdb_string_keys` to `false`)  appears not to be
needed anymore.

Update `.sync.yml` so that modulesync doesn't override this while the
default is still `false`

.sync.yml

@@ -1,7 +1,8 @@
 ---
 spec/spec_helper.rb:
-  spec_overrides: "require 'spec_helper_local'"
+  facterdb_string_keys: true
   mock_with: ':mocha'
+  spec_overrides: "require 'spec_helper_local'"
 .puppet-lint.rc:
   enabled_lint_checks:
     - parameter_documentation

spec/spec_helper.rb

@@ -10,7 +10,6 @@
 require 'voxpupuli/test/spec_helper'
 
 RSpec.configure do |c|
-  c.facterdb_string_keys = false
   c.mock_with :mocha
 end