fix the docs to fully document what is possible today

Author: aignas

docs/pypi-dependencies.md

@@ -348,6 +348,12 @@ pip.parse(
         "requirements.linux_x86_64.txt": "linux_x86_64",
         "requirements.osx_aarch64.txt": "osx_aarch64",
     },
+    # We need to set these values to ensure that the METADATA is
+    # correctly parsed after downloading wheels.
+    experimental_target_platforms = [
+        "cp39_linux_x86_64",
+        "cp39_osx_aarch64",
+    ],
 )
 ```