Correct URL in test_parse_dependency_specification

The URL path is used by `mock_download` to determine the path relative
to the fixtures directory to get the download result.

I believe this has been passing on CI because the `copy_or_symlink` call
in `mock_download` happily creates a symlink to a non-existent path, but
when running on Windows without permission to create symlinks,
`shutil.copyfile` is called as a fallback, and fails trying to copy a
non-existent file.

tests/utils/test_dependency_specification.py

@@ -46,8 +46,11 @@
         ("../demo", {"name": "demo", "path": "../demo"}),
         ("../demo/demo.whl", {"name": "demo", "path": "../demo/demo.whl"}),
         (
-            "https://example.com/packages/demo-0.1.0.tar.gz",
-            {"name": "demo", "url": "https://example.com/packages/demo-0.1.0.tar.gz"},
+            "https://example.com/distributions/demo-0.1.0.tar.gz",
+            {
+                "name": "demo",
+                "url": "https://example.com/distributions/demo-0.1.0.tar.gz",
+            },
         ),
         # PEP 508 inputs
         (