Use Ruby's Native JSON conversion rather than outputting a JSON string

i.e instead of:

``` ruby
body = " { \"a\": 123 }"
```

Do:

``` ruby
require 'json'
body = { a: 123 }.to_json
```

No files, tests, or entry points are named. Start by locating the Ruby snippet generator and its handling of request bodies, then compare its output with the examples in the issue. Done means Ruby snippets use native JSON conversion rather than manually formatted JSON strings.

Written by the indexing model from the issue text.