content: fix typo

Fixes golang/go#14550.

Change-Id: Ia908d10edf24260e3814787b44b28c91ddf9aae3
Reviewed-on: https://go-review.googlesource.com/20191
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/content/basics.article b/content/basics.article
index 2fd5945..230ddeb 100644
--- a/content/basics.article
+++ b/content/basics.article
@@ -157,7 +157,7 @@
 The zero value is:
 
 - `0` for numeric types,
-- `false` the boolean type, and
+- `false` for the boolean type, and
 - `""` (the empty string) for strings.
 
 .play basics/zero.go