Relax openslide pin

This was pinned to avoid `openslide` version `4` due to some solver
issues that cropped up with it. Namely it was missing `libdicom` (and an
associated version constraint). However this has been fixed upstream by
adding a repodata patch, adding `run_exports` to `libdicom` (was
missing), and adding a `libdicom` associated test in `openslide`. Given
this we should be able to relax the pin here, which this does.

conda/recipes/libcucim/meta.yaml

@@ -70,7 +70,7 @@ requirements:
     - jbig
     - libwebp-base
     - nvtx-c >=3.1.0
-    - openslide <4
+    - openslide
     - xz
     - zlib
     - zstd