Fix deprecation warning (template vs view in rspec-rails)

[pablobm]

We are getting the following warning when running this example:

template is deprecated. Use view instead. Called from
PATH/spec/administrate/views/fields/has_one/_show_spec.rb:56:in `block
(3 levels) in <top (required)>'.

If you need more of the backtrace for any of these deprecations to
identify where to make the necessary changes, you can configure
`config.raise_errors_for_deprecations!`, and it will turn the
deprecation warnings into errors, giving you the full backtrace.