Pin mslice at the minor level

This allows mslice nightly to be installed alongside mantidworkbench nightly.
The mechanism already exists for automatically switching between the nightly and main mantid labels.

Author: thomashampson

conda/recipes/conda_build_config.yaml

@@ -68,7 +68,7 @@ matplotlib:
   - 3.9.*
 
 mslice:
-  - '2.11.0'
+  - '2.11'
 
 
 ninja: