docs/process: branching-checklist: Remove reference to qemu-ijw.git

Per [1], qemu-iwj.git was a clone of QEMU traditional on Ian's computer
for tagging QEMU trad.

The next section will provide tag for the official tree. So remove
the section about qemu-ijw.git.

[1] 25482.10006.140155.984629@chiark.greenend.org.uk

Signed-off-by: Julien Grall <jgrall@amazon.com>
Acked-by: George Dunlap <george.dunlap@cloud.com>
Acked-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
Reviewed-by: Henry Wang <Henry.Wang@arm.com>

docs/process/branching-checklist.txt

@@ -1,9 +1,6 @@
 v=4.1
 ov=4.0
 
-* make branch in qemu-iwj.git
-    git-branch $v-testing master
-
 # make branches in xenbits.xen.org qemus
     ssh xen@xenbits.xen.org
     cd ~/git/qemu-xen.git