CI: Bring unit test jobs in line with 2024.1 tested runtimes

The last time I really looked at this was probably Yoga, when we were
targetting 3.6 through 3.9 (and left 3.7 and 3.8 as experimental jobs).

Now, though, OpenStack is targetting 3.8 through 3.11; as before, we
can assume that if tests pass on those two versions, they should pass
on the versions in-between, too. (But still have them as experimental,
on-demand jobs).

See https://governance.openstack.org/tc/reference/runtimes/2024.1.html

Keep 2.7 and 3.6 testing as our own self-imposed minimums.

Change-Id: I7700aa3c93df311644655e7ebaf0b67aa692ee80

.zuul.yaml

@@ -669,9 +669,7 @@
               - ^test/(cors|functional|probe|s3api)/.*$
         - swift-tox-py36:
             irrelevant-files: *unittest-irrelevant-files
-        - swift-tox-py39:
+        - swift-tox-py38:
-            irrelevant-files: *unittest-irrelevant-files
-        - swift-tox-py310:
             irrelevant-files: *unittest-irrelevant-files
         - swift-tox-py311:
             irrelevant-files: *unittest-irrelevant-files
@@ -761,8 +759,7 @@
             irrelevant-files: *docker-irrelevant-files
         - swift-tox-py27
         - swift-tox-py36
-        - swift-tox-py39
+        - swift-tox-py38
-        - swift-tox-py310
         - swift-tox-py311
         - swift-tox-func-py27
         - swift-tox-func-encryption-py27
@@ -795,7 +792,8 @@
     experimental:
       jobs:
         - swift-tox-py37
-        - swift-tox-py38
+        - swift-tox-py39
+        - swift-tox-py310
         - swift-tox-py36-centos-8-stream
         - swift-tox-func-py39-centos-9-stream
         - swift-tox-func-encryption-py39-centos-9-stream