Update IRIS CI to get minimal dependencies from conda channels

Author: yousefmoazzam

.github/workflows/run_tests_iris.yml

@@ -27,8 +27,10 @@ jobs:
       - name: Create conda environment
         uses: mamba-org/setup-micromamba@v1
         with:
-          environment-file: conda/environment.yml
           environment-name: httomo_backends
+          create-args: >-
+            cupy==12.3.0
+            ccpi::ccpi-regulariser
           post-cleanup: 'all'
           init-shell: bash