[ostream.inserters.arithmetic] Fix indentation

Author: Andreas-Krug

source/iostreams.tex

@@ -6433,7 +6433,7 @@
 the formatting conversion occurs as if it performed the following code fragment:
 \begin{codeblock}
 bool failed = use_facet<num_put<charT, ostreambuf_iterator<charT, traits>>>(
-    getloc()).put(*this, *this, fill(), val).failed();
+  getloc()).put(*this, *this, fill(), val).failed();
 \end{codeblock}
 
 When \tcode{val} is of type