Tweaked sqlite3 documentation

I thought this sentence was a little confusing when I was reading the docs, so I tweaked it a bit.

I also considered wording it as: "Now, to use the database, all an application must do is either have an active application context (which is always true if there is a request in flight) or create an application context itself." -> if emphasizing the "all an application must do" part seems quite important.

Totally understand if this PR seems trivial/unnecessary/etc; just wanted to try throwing it out there since it was helpful to me.

Thank you!