release: explicit predicate

Signed-off-by: William Woodruff <[email protected]>

Author: woodruffw

.github/workflows/release.yml

@@ -39,3 +39,4 @@ jobs:
           ./dist/*.tar.gz
           ./dist/*.whl
         predicate-type: 'https://docs.pypi.org/attestations/publish/v1'
+        predicate: '{}'