doc: fix note about Xen credit scheduler

Commit 6c504d6 added a note to the virsh man page about the
deprecation of 'cap' and 'weight' settings for the credit
scheduler. To this day, the default scheduler in Xen is credit
and it supports setting 'cap' and 'weight'. Remove the deprecation
notice from the note on the Xen credit scheduler.

Reported-by: Volo M. <vm@vovs.net>

tools/virsh.pod

@@ -1959,7 +1959,7 @@ Therefore, -1 is a useful shorthand for 262144. On the Linux kernel, the
 values 0 and 1 are automatically converted to a minimal value of 2.
 
 B<Note>: The weight and cap parameters are defined only for the
-XEN_CREDIT scheduler and are now I<DEPRECATED>.
+XEN_CREDIT scheduler.
 
 B<Note>: The vcpu_period, emulator_period, and iothread_period parameters
 have a valid value range of 1000-1000000 or 0, and the vcpu_quota,