Disable rollback tests for amd64

In commit 5bf3c4a9 tests for amd64 board were re enabled after adding
support for Up Squared 6000 board, and having enough boards in LAVA.

After this, it was seen that tests that relies in bootcount fail and
require a rework to align u-boot and uefi.

In the mean time, to avoid creating noise and masking issues disable
tests that rely in bootcount.

Signed-off-by: Walter Lozano <walter.lozano@collabora.com>

test-cases/aum-ota-rollback-blacklist.yaml

@@ -2,7 +2,7 @@ metadata:
   name: aum-ota-rollback-blacklist
   format: "Apertis Test Definition 1.0"
   image-types:
-    fixedfunction: [ armhf, arm64, amd64 ]
+    fixedfunction: [ armhf, arm64 ]
   image-deployment:
     - OSTree
   group: "aum-ota-rollback-blacklist"

test-cases/aum-rollback-blacklist.yaml

@@ -2,7 +2,7 @@ metadata:
   name: aum-rollback-blacklist
   format: "Apertis Test Definition 1.0"
   image-types:
-    fixedfunction: [ armhf, arm64, amd64 ]
+    fixedfunction: [ armhf, arm64 ]
   image-deployment:
     - OSTree
   group: "aum-rollback-blacklist"