[fs.op.create.symlink] Fix indentation (#8757)

Author: Andreas-Krug

source/iostreams.tex

@@ -17720,7 +17720,7 @@
 \begin{itemdecl}
 void filesystem::create_symlink(const path& to, const path& new_symlink);
 void filesystem::create_symlink(const path& to, const path& new_symlink,
-                    error_code& ec) noexcept;
+                                error_code& ec) noexcept;
 \end{itemdecl}
 
 \begin{itemdescr}