ci: udpate continue markers and explain why

Author: dimaqq

.github/workflows/test.yaml

@@ -114,7 +114,7 @@ jobs:
           # * test_ssh
           # * ...
           # - "3.6/beta"
-    continue-on-error: false  # don't ignore if tests against some juju version fail
+    continue-on-error: false  # ultimately fail a run if one of the matrix combinations fails
     steps:
       - name: Check out code
         uses: actions/checkout@v4
@@ -158,7 +158,7 @@ jobs:
       - name: Run integration
         # Force one single concurrent test
         run: tox -e integration
-        continue-on-error: true  # so that other juju versions are tested
+        continue-on-error: true  # don't fail early, let other matrix combinations get tested
 
   integration-quarantine:
     name: Quarantined Integration Tests
@@ -174,6 +174,7 @@ jobs:
           - "3.3/stable"
           - "3.4/stable"
           - "3.5/stable"
+    continue-on-error: false  # ultimately fail the run if one of the matrix combinations fails
     steps:
       - name: Check out code
         uses: actions/checkout@v3
@@ -188,4 +189,4 @@ jobs:
           juju-channel: ${{ matrix.juju }}
       - name: Run integration
         run: tox -e integration-quarantine
-        continue-on-error: true  # so that other juju versions are tested
+        continue-on-error: true  # don't fail early, let other matrix combinations get tested