Update background-tasks.md (#284)

Author: naomiaro

src/pages/postgraphile/background-tasks.md

@@ -60,14 +60,14 @@ Other important considerations when choosing a task queue would be:
 
 ### Graphile Worker
 
-Graphile Worker is a natural fit for a PostGraphile stack due to it's
+Graphile Worker is a natural fit for a PostGraphile stack due to its
 PostgreSQL-first nature. It is a simple library that runs Node.js code (or any
 code Node.js can delegate to) when a task is queued within the database. Thanks
 to PostgreSQL's `LISTEN/NOTIFY` pubsub features, Graphile Worker is notified
 when a task is queued and can fetch, execute, and complete a trivial task in
 2-3ms from when it was queued; this results in your system feeling very snappy.
 
-Graphile Worker stores tasks into it's own schema within PostgreSQL, and offers
+Graphile Worker stores tasks into its own schema within PostgreSQL, and offers
 a simple SQL API to create jobs. Queueing a job might look like:
 
 ```sql