content: fix typo in pipelines article

Change-Id: I3fe84b9929fa64585dec5b685b3383612a48ba24
Reviewed-on: https://go-review.googlesource.com/62110
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
diff --git a/content/pipelines.article b/content/pipelines.article
index 05772c9..a0fcb2c 100644
--- a/content/pipelines.article
+++ b/content/pipelines.article
@@ -151,7 +151,7 @@
 
 When `main` decides to exit without receiving all the values from
 `out`, it must tell the goroutines in the upstream stages to abandon
-the values they're trying it send.  It does so by sending values on a
+the values they're trying to send.  It does so by sending values on a
 channel called `done`.  It sends two values since there are
 potentially two blocked senders: