github: workflows: Update zephyr docker image

Should include a newer version of python as the old image python
version is no longer usable in zephyr

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

Author: nordicjm

.github/workflows/zephyr_build.yaml

@@ -40,12 +40,12 @@ jobs:
     runs-on: ubuntu-latest
     # Docker image from the zephyr upstream. Includes SDK and other required tools
     container:
-      image: zephyrprojectrtos/ci:v0.27.4
+      image: zephyrprojectrtos/ci:v0.27.6
       options: '--entrypoint /bin/bash'
       volumes:
         - /home/runners/zephyrproject:/github/cache/zephyrproject
     env:
-      ZEPHYR_SDK_INSTALL_DIR: /opt/toolchains/zephyr-sdk-0.17.0
+      ZEPHYR_SDK_INSTALL_DIR: /opt/toolchains/zephyr-sdk-0.17.1-rc2
 
     steps:
       - name: Set versions when workflow_dispatch