go.blog/slices: fix mistake in length of slice2.

R=adg
CC=golang-dev
https://golang.org/cl/14013045
diff --git a/content/slices.article b/content/slices.article
index f2dd073..eb974e8 100644
--- a/content/slices.article
+++ b/content/slices.article
@@ -129,7 +129,7 @@
 this:
 
 	slice2 := sliceHeader{
-		Length:        10,
+		Length:        5,
 		ZerothElement: &buffer[105],
 	}
 
@@ -474,7 +474,7 @@
 * Nil
 
 As an aside, with our newfound knowledge we can see what the representation of a `nil` slice is.
-Of course, it is the zero value of the slice header:
+Naturally, it is the zero value of the slice header:
 
 	sliceHeader{
 		Length:        0,