Revert "Fix references to version.py -> europi_version.py"

This reverts commit a0ae9f5.

Author: chrisib

software/firmware/europi_version.py

@@ -12,4 +12,4 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 """EuroPi firmware and contrib package version"""
-__version__ = "0.23.0"
+__version__ = "0.23.1"