Fixing python version

mantid-nightly.def

@@ -51,9 +51,7 @@ From: ubuntu:22.04
                  libxrandr2
 
   # Installing mantid
-  conda create -n mantid-singularity python=3.8
-  conda activate mantid-singularity
-  conda install -c mantid/label/nightly -c conda-forge  mantidworkbench
+  conda create -n mantid-singularity -c mantid/label/nightly -c conda-forge  mantidworkbench
   conda clean -ya
   echo ". /opt/conda/etc/profile.d/conda.sh" >> $SINGULARITY_ENVIRONMENT
   echo "conda activate mantid-singularity" >> $SINGULARITY_ENVIRONMENT