Documentation/RCU: Fix nested inline markup

To avoid the ``foo`` markup inside the `bar`__ hyperlink marker,
use the "replace" directive [1].

This should restore the intended appearance of the link.

Tested with sphinx versions 1.7.9 and 2.4.4.

[1]: https://docutils.sourceforge.io/docs/ref/rst/directives.html#replaceSigned-off-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Documentation/RCU/Design/Requirements/Requirements.rst

@@ -362,9 +362,8 @@ do_something_gp() uses rcu_dereference() to fetch from ``gp``:
       12 }
 
 The rcu_dereference() uses volatile casts and (for DEC Alpha) memory
-barriers in the Linux kernel. Should a `high-quality implementation of
-C11 ``memory_order_consume``
-[PDF] <http://www.rdrop.com/users/paulmck/RCU/consume.2015.07.13a.pdf>`__
+barriers in the Linux kernel. Should a |high-quality implementation of
+C11 memory_order_consume [PDF]|_
 ever appear, then rcu_dereference() could be implemented as a
 ``memory_order_consume`` load. Regardless of the exact implementation, a
 pointer fetched by rcu_dereference() may not be used outside of the
@@ -374,6 +373,9 @@ element has been passed from RCU to some other synchronization
 mechanism, most commonly locking or `reference
 counting <https://www.kernel.org/doc/Documentation/RCU/rcuref.txt>`__.
 
+.. |high-quality implementation of C11 memory_order_consume [PDF]| replace:: high-quality implementation of C11 ``memory_order_consume`` [PDF]
+.. _high-quality implementation of C11 memory_order_consume [PDF]: http://www.rdrop.com/users/paulmck/RCU/consume.2015.07.13a.pdf
+
 In short, updaters use rcu_assign_pointer() and readers use
 rcu_dereference(), and these two RCU API elements work together to
 ensure that readers have a consistent view of newly added data elements.