Update to actions/cache@v4 to account for deprecation of Node 16

Node.js 16 actions are deprecated. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

.github/workflows/pipeline.yml

@@ -46,7 +46,7 @@ jobs:
           channels: conda-forge,
 
       - name: Cache conda
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         env:
           # Increase this value to reset cache if environment.yml has not changed
           CACHE_NUMBER: 0