docs/about/removed-features: auto-generate a note for versioned machine types

We remove versioned machine types on a fixed schedule. This allows us
to auto-generate a paragraph in the removed-features.rst document that
always has accurate version info.

Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
diff --git a/docs/conf.py b/docs/conf.py
index 60dcf2a..248ff8c 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -137,6 +137,7 @@
         minor += 1
 
 ver_machine_deprecation_version = "%d.%d.0" % (major - 3, minor)
+ver_machine_deletion_version = "%d.%d.0" % (major - 6, minor)
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
@@ -170,6 +171,7 @@
 vars = {
     "CONFDIR": confdir,
     "VER_MACHINE_DEPRECATION_VERSION": ver_machine_deprecation_version,
+    "VER_MACHINE_DELETION_VERSION": ver_machine_deletion_version,
 }
 
 rst_epilog = "".join([