Update overview.rst | Fix an inconsistency

There exists an inconsistency between the code (line 37 - 38) and the output 'quotes.json' (line 56 - 68). 

Note that even though according to line 53 - 54  'quotes.json' is "reformatted here for better readability", it cannot explain why the "author" field precedes the "text" field. 

Intended output for the code BEFORE change: 
    [{
        "text": "\u201cThe person, be it gentleman or lady, who has not pleasure in a good novel, must be intolerably stupid.\u201d",
        "author": "Jane Austen"
    },
    {
        "text": "\u201cOutside of a dog, a book is man's best friend. Inside of a dog it's too dark to read.\u201d",
        "author": "Groucho Marx"
    },
    {
        "text": "\u201cA day without sunshine is like, you know, night.\u201d",
        "author": "Steve Martin"
    },
    ...]

Intended output for the code After change (the inconsistency is fixed): 
    [{
        "author": "Jane Austen",
        "text": "\u201cThe person, be it gentleman or lady, who has not pleasure in a good novel, must be intolerably stupid.\u201d"
    },
    {
        "author": "Groucho Marx",
        "text": "\u201cOutside of a dog, a book is man's best friend. Inside of a dog it's too dark to read.\u201d"
    },
    {
        "author": "Steve Martin",
        "text": "\u201cA day without sunshine is like, you know, night.\u201d"
    },
    ...]

docs/intro/overview.rst

@@ -34,8 +34,8 @@ http://quotes.toscrape.com, following the pagination::
         def parse(self, response):
             for quote in response.css('div.quote'):
                 yield {
-                    'text': quote.css('span.text::text').get(),
                     'author': quote.xpath('span/small/text()').get(),
+                    'text': quote.css('span.text::text').get(),
                 }
 
             next_page = response.css('li.next a::attr("href")').get()