Fix readability issues with before_record hook docs

From: https://www.relishapp.com/vcr/vcr/v/2-8-0/docs/hooks/before-record-hook

> You can also call `#ignore!` on the HTTP interaction to prevent VCR
from recording it.
>
> If you don't your hook to apply to all cassettes, you can use tags for
this purpose. Consider this code:

The paragraph before these two talk about the arguments a block must accept. The transition to the ability to call `#ignore!` on the interaction doesn't make much sense. The paragraph after it, doesn't make sense either. 

I suspect the two paragraphs should have been in reverse order but I fixed the wording since the example for the second paragraph follows it.