DPE-4556 Bump Juju version to the lastest patchset level of 2.9/3.1 (#457)

* DPE-4556 Bump Juju version to the lastest patchset level of 2.9/3.1

* Apply suggestions from code review

---------

Co-authored-by: Carl Csaposs <[email protected]>

Author: taurus-forever

.github/workflows/ci.yaml

@@ -65,10 +65,10 @@ jobs:
       fail-fast: false
       matrix:
         juju:
-          - agent: 2.9.46
+          - agent: 2.9.49  # renovate: juju-agent-pin-minor
             libjuju: ^2
             allure: false
-          - agent: 3.1.7
+          - agent: 3.1.8  # renovate: juju-agent-pin-minor
             allure: true
     name: Integration test charm | ${{ matrix.juju.agent }}
     needs: