Pin the conda recipe to the RaPDTool-v2.3.1 tag

A branch ref can move; the tag cannot, so a rebuild of this recipe always
resolves to the same tree.

Author: Karel

conda-recipe/meta.yaml

@@ -4,7 +4,7 @@ package:
 
 source:
   git_url: https://github.com/BioTools-Dev/RaPDTool.git
-  git_rev: v2.3.1          # pin to the release branch/tag so the build is reproducible
+  git_rev: RaPDTool-v2.3.1 # release tag: immutable, so the build is reproducible
 
 build:
   number: 0