manifest: remove obsolete kvmtool repo

kvmtool is no longer needed since we now have crosvm. Remove it from
the manifest.

BUG=none
TEST=repo sync

Change-Id: I7031f08b746caa1a52e9a2f796a1fb17d6021fb4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/manifest/+/1648937Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
Commit-Queue: Stephen Barber <smbarber@chromium.org>
Tested-by: Stephen Barber <smbarber@chromium.org>

full.xml

@@ -300,8 +300,6 @@ Your sources have been sync'd successfully.
            revision="refs/heads/chromeos-4.19" />
   <project path="src/third_party/khronos"
            name="chromiumos/third_party/khronos" />
-  <project path="src/third_party/kvmtool"
-           name="chromiumos/third_party/kvmtool" />
   <project path="src/third_party/libapps"
            name="apps/libapps">
     <annotation name="branch-mode" value="pin" />