Documentation: KVM: fix warning in "make htmldocs"

The warning

 Documentation/virt/kvm/locking.rst:31: ERROR: Unexpected indentation.

is caused by incorrectly treating a line as the continuation of a paragraph,
rather than as the first line in a bullet list.

Fixed: 44d17459 ("KVM: Use dedicated mutex to protect kvm_usage_count to avoid deadlock")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Documentation/virt/kvm/locking.rst

@@ -27,6 +27,7 @@ The acquisition orders for mutexes are as follows:
   must not take either kvm->slots_lock or kvm->slots_arch_lock.
 
 cpus_read_lock() vs kvm_lock:
+
 - Taking cpus_read_lock() outside of kvm_lock is problematic, despite that
   being the official ordering, as it is quite easy to unknowingly trigger
   cpus_read_lock() while holding kvm_lock.  Use caution when walking vm_list,