[troubleshooting] hiera

Fix the display for "note" in "Find the value hiera returns to puppet" doc part.

```
  *note* -> .. note:: like other note in page http://spinal-stack.readthedocs.org/en/latest/deploy/introduction.html#requirements
  `code` -> ``code`` (Display inline code https://pythonhosted.org/an_example_pypi_project/sphinx.html#code)
```