[fs.op.copy.file] Fix indentation (#8024)

Author: Andreas-Krug

source/iostreams.tex

@@ -17432,7 +17432,7 @@
 \begin{itemdecl}
 bool filesystem::copy_file(const path& from, const path& to, copy_options options);
 bool filesystem::copy_file(const path& from, const path& to, copy_options options,
-               error_code& ec);
+                           error_code& ec);
 \end{itemdecl}
 
 \begin{itemdescr}