content: fix typo in strings.Reader slide

Fixes golang/go#13962

Change-Id: I2a35d67677bd4a4267fedf542428267ece22b52e
Reviewed-on: https://go-review.googlesource.com/18793
Reviewed-by: Francesc Campoy Flores <campoy@golang.org>
diff --git a/content/methods.article b/content/methods.article
index 67c381e..bb40024 100644
--- a/content/methods.article
+++ b/content/methods.article
@@ -354,7 +354,7 @@
 ends.
 
 The example code creates a 
-[[//golang.org/pkg/strings/#Reader][`strings.Reader`]].
+[[//golang.org/pkg/strings/#Reader][`strings.Reader`]]
 and consumes its output 8 bytes at a time.
 
 .play methods/reader.go