[fs.op.last.write.time] Fix indentation

Author: Andreas-Krug

source/iostreams.tex

@@ -18276,7 +18276,7 @@
 \begin{itemdecl}
 void filesystem::last_write_time(const path& p, file_time_type new_time);
 void filesystem::last_write_time(const path& p, file_time_type new_time,
-                     error_code& ec) noexcept;
+                                 error_code& ec) noexcept;
 \end{itemdecl}
 
 \begin{itemdescr}