doc: add missing preposition in go1.5.html

Change-Id: I2f855b9ad1676b3c4efedd764ce99e21c104a4ec
Reviewed-on: https://go-review.googlesource.com/12446Reviewed-by: Rob Pike <r@golang.org>

doc/go1.5.html

@@ -778,7 +778,7 @@ Also in the <a href="/pkg/bytes/"><code>bytes</code></a> package,
 the <a href="/pkg/bytes/#Buffer"><code>Buffer</code></a> type
 now has a <a href="/pkg/bytes/#Buffer.Cap"><code>Cap</code></a> method
 that reports the number of bytes allocated within the buffer.
-Similarly, both the <a href="/pkg/bytes/"><code>bytes</code></a>
+Similarly, in both the <a href="/pkg/bytes/"><code>bytes</code></a>
 and <a href="/pkg/strings/"><code>strings</code></a> packages,
 the <a href="/pkg/bytes/#Reader"><code>Reader</code></a>
 type now has a <a href="/pkg/bytes/#Reader.Size"><code>Size</code></a>