CI: exclude rootfs from artifact uploads

Rootfs directories contain files with mapped UIDs that the runner
can't read, breaking the artifact zip upload.

Signed-off-by: Matej Hrica <mhrica@redhat.com>

Author: mtjhrc

.github/workflows/integration_tests.yml

@@ -68,7 +68,7 @@ jobs:
           path: |
             /tmp/libkrun-tests/
             !/tmp/libkrun-tests/**/guest-agent
-ROOTFS_PLACEHOLDER
+            !/tmp/libkrun-tests/**/rootfs
           if-no-files-found: ignore
 
   integration-tests-aarch64:
@@ -133,5 +133,5 @@ ROOTFS_PLACEHOLDER
           path: |
             /tmp/libkrun-tests/
             !/tmp/libkrun-tests/**/guest-agent
-ROOTFS_PLACEHOLDER
+            !/tmp/libkrun-tests/**/rootfs
           if-no-files-found: ignore