Reverting broken change.

Reverting change that seems to be preventing tests from passing.

.github/workflows/iriscast_package_build.yaml

@@ -67,7 +67,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: ["3.x", "3.10", "3.6.8"]
+        python-version: ["3.10", "3.6.8"]
     steps:
       - uses: actions/checkout@v4
       - name: Set up Python ${{ matrix.python-version }}