MNT: Unpin libitk 5.3 (ANTs 2.5.3 is built with 5.4)

Author: effigies

env.yml

@@ -12,8 +12,6 @@ dependencies:
   - mkl-service=2.4.0
   # git-annex for templateflow users with DataLad superdatasets
   - git-annex=*=alldep*
-  # ANTs is linked against libitk 5.3 but does not pin the version
-  - libitk=5.3
   # Base scientific python stack; required by FSL, so pinned here
   - numpy=1.26
   - scipy=1.13