spack checksum: warn if version is deprecated (#32438)

Co-authored-by: Massimiliano Culpo <massimiliano.culpo@gmail.com>

lib/spack/docs/conf.py

@@ -206,6 +206,8 @@ def setup(sphinx):
     # Spack classes that are private and we don't want to expose
     ("py:class", "spack.provider_index._IndexBase"),
     ("py:class", "spack.repo._PrependFileLoader"),
+    # Spack classes that intersphinx is unable to resolve
+    ("py:class", "spack.version.VersionBase"),
 ]
 
 # The reST default role (used for this markup: `text`) to use for all documents.