docs/misc: xen-command-line: Remove wrong statement from serrors=diverse

When serrors=diverse is selected by the user, we will only synchronize
the pending SErrors on entry to hypervisor from guest context and exit
from guest to hypervisor context.

We don't need synchronize SErrors between guest context switch as they
would be categorized to Hypervisor generated SErrors in any case.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Release-acked-by: Juergen Gross <jgross@suse.com>
(cherry picked from commit 575186163c)

docs/misc/xen-command-line.pandoc

@@ -1845,7 +1845,6 @@ hypervisors handle SErrors:
   1. dsb/isb on all EL1 -> EL2 trap entries to categorize SErrors correctly.
   2. dsb/isb on EL2 -> EL1 return paths to prevent slipping hypervisor
      SErrors to guests.
-  3. dsb/isb in context switch to isolate SErrors between 2 vCPUs.
 
 * `forward`:
   The hypervisor will not distinguish guest SErrors from hypervisor SErrors.