Use latest UM from dev-access-esm1.6 branch

See [this](#43 (comment)) and subsequent comments for justification

Author: dougiesquire

spack.yaml

@@ -20,7 +20,7 @@ spack:
         - '@git.update_DaveBi=access-esm1.5'
     um7:
       require:
-        - '@git.dev-access-esm1.6=access-esm1.6'
+        - '@git.86a4e1fc37cb1d6fc1dae536deb5c0bd104506bf=access-esm1.6'
     gcom4:
       require:
         - '@git.2024.05.28=access-esm1.5'
@@ -68,7 +68,7 @@ spack:
         projections:
           access-esm1p6: '{name}/dev_2025.03.0'
           cice4: '{name}/update_DaveBi-{hash:7}'
-          um7: '{name}/dev-access-esm1.6-{hash:7}'
+          um7: '{name}/86a4e1fc37cb1d6fc1dae536deb5c0bd104506bf-{hash:7}'
           mom5: '{name}/dev-2025.03.001-{hash:7}'
   config:
     install_tree: