(CAT-2484) Fix rspec warning.

This commit fixes the following warning that appeared at the top of the rspec output:

```
WARNING: `around(:context)` hooks are not supported and behave like `around(:example)`. Called from ...
```

Signed-off-by: Gavin Didrichsen <[email protected]>

Author: gavindidrichsen

spec/unit/puppet-lint/bin_spec.rb

@@ -635,7 +635,7 @@ def initialize(args)
 
   context 'when overriding config file options with command line options' do
     context 'and config file sets "--only-checks=variable_contains_dash"' do
-      around(:context) do |example|
+      around(:each) do |example|
         Dir.mktmpdir do |tmpdir|
           Dir.chdir(tmpdir) do
             File.open('.puppet-lint.rc', 'wb') do |f|