rcutorture: Remove CONFIG_RCU_USER_QS from rcutorture selftest doc

Commit d1ec4c34 ("rcu: Drop RCU_USER_QS in favor of NO_HZ_FULL") has
removed RCU_USER_QS from Kconfig file, so remove it from some documents
to avoid any confusion.
Signed-off-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

tools/testing/selftests/rcutorture/doc/TINY_RCU.txt

@@ -20,7 +20,6 @@ CONFIG_PROVE_RCU
 
 CONFIG_NO_HZ_FULL_SYSIDLE
 CONFIG_RCU_NOCB_CPU
-CONFIG_RCU_USER_QS
 
 	Meaningless for TINY_RCU.
 

tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt

@@ -72,10 +72,6 @@ CONFIG_RCU_TORTURE_TEST_RUNNABLE
 
 	Always used in KVM testing.
 
-CONFIG_RCU_USER_QS
-
-	Redundant with CONFIG_NO_HZ_FULL.
-
 CONFIG_PREEMPT_RCU
 CONFIG_TREE_RCU