Remove concurrency groups for now. They seem to cause CI hangs

.github/workflows/main_matrix.yml

@@ -1,7 +1,7 @@
 name: CI
-concurrency:
-  group: ${{ github.ref }}
-  cancel-in-progress: ${{ github.ref != 'refs/heads/master' }}
+#concurrency:
+#  group: ${{ github.ref }}
+#  cancel-in-progress: ${{ github.ref != 'refs/heads/master' }}
 on:
   # # Triggers the workflow on push but only for the master branch
   push: