PR checks: stop running unset-env on two old CLI versions

Looks like there was a bug in the oldest two CLI versions, on `macos-12` here.

.github/workflows/__unset-environment.yml

@@ -28,20 +28,16 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: macos-12
-            version: stable-20230403
-          - os: macos-12
-            version: stable-v2.13.5
           - os: macos-12
             version: stable-v2.14.6
           - os: macos-latest
             version: stable-v2.15.5
           - os: macos-latest
             version: stable-v2.16.6
-          - os: macos-latest
-            version: default
           - os: macos-latest
             version: latest
+          - os: macos-latest
+            version: default
           - os: macos-latest
             version: nightly-latest
     name: Test unsetting environment variables

pr-checks/checks/unset-environment.yml

@@ -1,5 +1,7 @@
 name: "Test unsetting environment variables"
 description: "An end-to-end integration test that unsets some environment variables"
+# TODO: Switch back to all versions once CLI v2.17.4 is available and running on ubuntu again.
+versions: ["stable-v2.14.6", "stable-v2.15.5", "stable-v2.16.6", "latest", "default", "nightly-latest"] 
 operatingSystems: ["macos"] # TODO: Switch back to ubuntu for `nightly-latest` and `latest` once CLI v2.17.4 is available.
 steps:
   - uses: ./../action/init