Another change which doesn't fail any tests.

This one is suspicious looking (which I saw while writing it)
but we'll force it back again by adding tests if it's indeed
correct.

Author: Julian

referencing/_core.py

@@ -241,14 +241,14 @@ def lookup(self, ref: str) -> tuple[Schema, Resolver]:
                 if not isinstance(target, Sequence):
                     id = resource._specification.id_of(target)
                     if id is not None:
-                        base_uri = urljoin(base_uri, id).rstrip("#")
+                        base_uri = urljoin(base_uri, id)
         elif fragment:
             resource, uri = anchors[fragment].resolve(resolver=self, uri=uri)
             target = resource.resource
 
             id = resource.id()
             if id is not None:
-                base_uri = urljoin(self._base_uri, id).rstrip("#")
+                base_uri = urljoin(self._base_uri, id)
         else:
             id = resource.id()
             if id is not None: