doc/RCU/Design: Remove remaining HTML tags in ReST files

Commit ccc9971e ("docs: rcu: convert some articles from html to
ReST") has converted a few of html RCU docs into ReST files, but a few
of html tags which not supported on rst is remaining.  This commit
converts those to ReST appropriate alternatives.
Reviewed-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst

@@ -4,7 +4,7 @@ A Tour Through TREE_RCU's Grace-Period Memory Ordering
 
 August 8, 2017
 
-This article was contributed by Paul E. McKenney
+This article was contributed by Paul E. McKenney
 
 Introduction
 ============
@@ -48,7 +48,7 @@ Tree RCU Grace Period Memory Ordering Building Blocks
 
 The workhorse for RCU's grace-period memory ordering is the
 critical section for the ``rcu_node`` structure's
-``->lock``. These critical sections use helper functions for lock
+``->lock``. These critical sections use helper functions for lock
 acquisition, including ``raw_spin_lock_rcu_node()``,
 ``raw_spin_lock_irq_rcu_node()``, and ``raw_spin_lock_irqsave_rcu_node()``.
 Their lock-release counterparts are ``raw_spin_unlock_rcu_node()``,
@@ -102,9 +102,9 @@ lock-acquisition and lock-release functions::
    23   r3 = READ_ONCE(x);
    24 }
    25
-   26 WARN_ON(r1 == 0 && r2 == 0 && r3 == 0);
+   26 WARN_ON(r1 == 0 && r2 == 0 && r3 == 0);
 
-The ``WARN_ON()`` is evaluated at “the end of time”,
+The ``WARN_ON()`` is evaluated at "the end of time",
 after all changes have propagated throughout the system.
 Without the ``smp_mb__after_unlock_lock()`` provided by the
 acquisition functions, this ``WARN_ON()`` could trigger, for example