Recall configs metadata should be an empty dictionary by default

[pieroit]

Having an empty dictionary will allow devs to avoid checking for not none:
https://github.com/cheshire-cat-ai/core/blob/f14f2c0acebddd3f1f1efb6ba3b161bea45e9e3a/core/cat/looking_glass/stray_cat.py#L224C25-L224C29

P.S.: check if the Qdrant recall does not mess up if we pass an empty dict