Revert "ci: when testing, install python 3.12, required by zephyr now"

This reverts commit e22db85 because
the Zephyr change increasing the minimum required Python version from
3.10 to 3.12 was reverted.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

Author: stephanosio

.github/workflows/ci.yml

@@ -343,19 +343,19 @@ jobs:
 
         if [ "${build_host_linux_x86_64}" == "y" ]; then
           MATRIX_TESTENVS+='{
-              "name": "ubuntu-24.04-x86_64",
+              "name": "ubuntu-20.04-x86_64",
               "runner": "zephyr-runner-v2-linux-x64-4xlarge",
-              "container": "ghcr.io/zephyrproject-rtos/ci:main",
+              "container": "ghcr.io/zephyrproject-rtos/ci:master",
               "bundle-host": "linux-x86_64",
               "bundle-archive": "tar.xz"
             },'
         fi
 
         if [ "${build_host_linux_aarch64}" == "y" ]; then
           MATRIX_TESTENVS+='{
-              "name": "ubuntu-24.04-aarch64",
+              "name": "ubuntu-20.04-aarch64",
               "runner": "zephyr-runner-v2-linux-arm64-4xlarge",
-              "container": "ghcr.io/zephyrproject-rtos/ci:main",
+              "container": "ghcr.io/zephyrproject-rtos/ci:master",
               "bundle-host": "linux-aarch64",
               "bundle-archive": "tar.xz"
             },'
@@ -1310,11 +1310,12 @@ jobs:
 
     steps:
     - name: Set up Python
+      if: ${{ runner.os == 'Windows' }}
       uses: actions/setup-python@v5
       with:
-        # Force Python 3.12, which is the minimum Python version supported by
-        # Zephyr and intended to be used with Zephyr SDK.
-        python-version: '3.12'
+        # Force Python 3.10 because the twister is not compatible with a Python
+        # version lower than 3.8 on Windows.
+        python-version: '3.10'
 
     - name: Set up test environment (Linux)
       if: ${{ runner.os == 'Linux' }}
@@ -1510,8 +1511,6 @@ jobs:
           # if running inside a virtual environment; otherwise, it is assumed
           # that the host already provides all the required dependencies.
           pip3 install -r ${ZEPHYR_ROOT}/scripts/requirements.txt
-        else
-          pip3 install -r ${ZEPHYR_ROOT}/scripts/requirements-actions.txt --require-hashes
         fi
 
     - name: Run test suites