test(spread): run storage-detaching on juju36 as a no-regression guard

The task ran only on juju40 (where #1550 reproduces). Add juju36 so the teardown change (stopping/disabling the snap in storage-detaching) is also exercised on 3.6, where the bug is masked by force-removal but a new breakage would still surface.

Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>

Author: marceloneppel

tests/spread/test_storage_detaching.py/task.yaml

@@ -2,10 +2,9 @@ summary: test_storage_detaching.py
 environment:
   TEST_MODULE: test_storage_detaching.py
   # #1550 only reproduces on Juju 4.0 (3.6 masks it by removing still-Dying storage),
-  # so pin this task to a juju40 variant and drop the default juju36.
+  # so juju40 is the real regression test. Run juju36 too as a no-regression guard:
+  # stopping/disabling the snap in storage-detaching must not break 3.6 teardown.
   CONCIERGE_JUJU_CHANNEL/juju40: 4.0/stable
-variants:
-  - -juju36
 execute: |
   tox run -e integration -- "tests/integration/$TEST_MODULE" --model testing --alluredir="$SPREAD_TASK/allure-results"
 artifacts: