[fs.op.copy.symlink] Fix indentation

Author: Andreas-Krug

source/iostreams.tex

@@ -17495,7 +17495,7 @@
 \begin{itemdecl}
 void filesystem::copy_symlink(const path& existing_symlink, const path& new_symlink);
 void filesystem::copy_symlink(const path& existing_symlink, const path& new_symlink,
-                  error_code& ec) noexcept;
+                              error_code& ec) noexcept;
 \end{itemdecl}
 
 \begin{itemdescr}