[Docs] 2 typos + 1 clarification in docs
[Docs] 2 typos + 1 clarification in docs

Fixing 2 small typos and adding 1 word as clarification in the downloader-middlewares.

Also, I was confused with the entries like `ref:Reppy <reppy-parser>` and similar entries.
Are these supposed to be links to other parts of the doc, or is this the intended way of showing these references ?
dangra/scrapy,pablohoffman/scrapy,dangra/scrapy,elacuesta/scrapy,pawelmhm/scrapy,pawelmhm/scrapy,elacuesta/scrapy,pawelmhm/scrapy,pablohoffman/scrapy,scrapy/scrapy,starrify/scrapy,eLRuLL/scrapy,scrapy/scrapy,pablohoffman/scrapy,scrapy/scrapy,starrify/scrapy,starrify/scrapy,elacuesta/scrapy,eLRuLL/scrapy,eLRuLL/scrapy,dangra/scrapy