docs/arm-cpu-features: Make kvm-no-adjvtime comment clearer

The bold text sounds like 'knock knock'. Only bolding the
second 'not' makes it easier to read.

Fixes: dea101a1ae
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Message-id: 20200206225148.23923-1-philmd@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

docs/arm-cpu-features.rst

@@ -185,7 +185,7 @@ the list of KVM VCPU features and their descriptions.
 
   kvm-no-adjvtime          By default kvm-no-adjvtime is disabled.  This
                            means that by default the virtual time
-                           adjustment is enabled (vtime is *not not*
+                           adjustment is enabled (vtime is not *not*
                            adjusted).
 
                            When virtual time adjustment is enabled each