Jenkinsfile: Re-enable the minimal ostree images

They got disabled during in the early phases of the Buster rebase, we should
start buidling them again now.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>

Jenkinsfile

@@ -39,7 +39,7 @@ def architectures = [
                 args: "-t demopack:${demopack}",
                 image: true,
                 sysroot: false,
-                //ostree: true,
+                ostree: true,
             ],
             target: [
                 args: "-t demopack:${demopack}",
@@ -83,7 +83,7 @@ def architectures = [
                 args: "-t demopack:${demopack}",
                 image: true,
                 sysroot: false,
-                //ostree: true,
+                ostree: true,
             ],
             target: [
                 args: "-t demopack:${demopack}",
@@ -106,7 +106,7 @@ def architectures = [
                 args: "-t demopack:${demopack}",
                 image: true,
                 sysroot: false,
-                //ostree: true
+                ostree: true
             ],/*
             sysroot: [
                 args: '--scratchsize 10G',