fix(manager/poetry): fix schema for optional dependencies (#32096)

lib/modules/manager/poetry/__fixtures__/pyproject.1.toml

lib/modules/manager/poetry/__fixtures__/pyproject.2.toml

...modules/manager/poetry/__snapshots__/extract.spec.ts.snap

lib/modules/manager/poetry/extract.spec.ts

lib/modules/manager/poetry/schema.ts

lib/util/schema-utils.ts