[saferecl.rcu.domain.func] Fix indentation

Author: Andreas-Krug

source/threads.tex

@@ -13216,7 +13216,7 @@
 \indexlibraryglobal{rcu_retire}%
 \begin{itemdecl}
 template<class T, class D = default_delete<T>>
-void rcu_retire(T* p, D d = D(), rcu_domain& dom = rcu_default_domain());
+  void rcu_retire(T* p, D d = D(), rcu_domain& dom = rcu_default_domain());
 \end{itemdecl}
 
 \begin{itemdescr}