[span.overview] Fix typo (#2059)

tcbrindle · tkoeppe · commit e22fff1b8d8b · 2018-05-04T19:59:09.000+01:00
nnamespace -&gt; namespace
diff --git a/source/containers.tex b/source/containers.tex
@@ -9759,7 +9759,7 @@
 
 \indexlibrary{\idxcode{span}}%
 \begin{codeblock}
-nnamespace std {
+namespace std {
   template<class ElementType, ptrdiff_t Extent = dynamic_extent>
   class span {
   public:
