Tweak description of versioning to use new Apertis string

We are now beginning to use "+apertisX" rather than "coX" for Apertis changes.
Tweak the description of versioning to use this new string.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>

content/guides/buildingpatchingandmaintainingtheapertiskernel.md

@@ -770,9 +770,9 @@ The updated nature of the package is reflected in the version number
 given to the package and this will have an impact on the version number
 that should be assigned to the newly rebased tree (new upstream, plus or
 or more local changes). As an example will assume 3 local revisions have
-been made since the last rebase on `4.19.37-5co4`, following our
-previous example the version would expected to be `4.19.37-5co4foo3`,
-should a new Apertis release be made (`4.19.37-5co5`) and assuming that
+been made since the last rebase on `4.19.37-5+apertis4`, following our
+previous example the version would expected to be `4.19.37-5+apertis4foo3`,
+should a new Apertis release be made (`4.19.37-5+apertis5`) and assuming that
 the local changes are still needed, then the local version with these
 inclusions with constitute the first local release on top of the new
-upstream, thus becoming `4.19.37-5co5foo1`.
+upstream, thus becoming `4.19.37-5+apertis5foo1`.